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js/goog/events/browserevent.js

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+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A patched, standardized event object for browser events.
+ *
+ * <pre>
+ * The patched event object contains the following members:
+ * - type           {string}    Event type, e.g. 'click'
+ * - target         {Object}    The element that actually triggered the event
+ * - currentTarget  {Object}    The element the listener is attached to
+ * - relatedTarget  {Object}    For mouseover and mouseout, the previous object
+ * - offsetX        {number}    X-coordinate relative to target
+ * - offsetY        {number}    Y-coordinate relative to target
+ * - clientX        {number}    X-coordinate relative to viewport
+ * - clientY        {number}    Y-coordinate relative to viewport
+ * - screenX        {number}    X-coordinate relative to the edge of the screen
+ * - screenY        {number}    Y-coordinate relative to the edge of the screen
+ * - button         {number}    Mouse button. Use isButton() to test.
+ * - keyCode        {number}    Key-code
+ * - ctrlKey        {boolean}   Was ctrl key depressed
+ * - altKey         {boolean}   Was alt key depressed
+ * - shiftKey       {boolean}   Was shift key depressed
+ * - metaKey        {boolean}   Was meta key depressed
+ * - pointerId      {number}    Pointer ID
+ * - pointerType    {string}    Pointer type, e.g. 'mouse', 'pen', or 'touch'
+ * - defaultPrevented {boolean} Whether the default action has been prevented
+ * - state          {Object}    History state object
+ *
+ * NOTE: The keyCode member contains the raw browser keyCode. For normalized
+ * key and character code use {@link goog.events.KeyHandler}.
+ * </pre>
+ */
+
+goog.provide('goog.events.BrowserEvent');
+goog.provide('goog.events.BrowserEvent.MouseButton');
+goog.provide('goog.events.BrowserEvent.PointerType');
+
+goog.require('goog.debug');
+goog.require('goog.events.Event');
+goog.require('goog.events.EventType');
+goog.require('goog.reflect');
+goog.require('goog.userAgent');
+
+/**
+ * @define {boolean} If true, use the layerX and layerY properties of a native
+ * browser event over the offsetX and offsetY properties, which cause expensive
+ * reflow. If layerX or layerY is not defined, offsetX and offsetY will be used
+ * as usual.
+ */
+goog.events.USE_LAYER_XY_AS_OFFSET_XY =
+    goog.define('goog.events.USE_LAYER_XY_AS_OFFSET_XY', false);
+
+/**
+ * Accepts a browser event object and creates a patched, cross browser event
+ * object.
+ * The content of this object will not be initialized if no event object is
+ * provided. If this is the case, init() needs to be invoked separately.
+ * @param {Event=} opt_e Browser event object.
+ * @param {EventTarget=} opt_currentTarget Current target for event.
+ * @constructor
+ * @extends {goog.events.Event}
+ */
+goog.events.BrowserEvent = function(opt_e, opt_currentTarget) {
+  'use strict';
+  goog.events.BrowserEvent.base(this, 'constructor', opt_e ? opt_e.type : '');
+
+  /**
+   * Target that fired the event.
+   * @override
+   * @type {?Node}
+   */
+  this.target = null;
+
+  /**
+   * Node that had the listener attached.
+   * @override
+   * @type {?Node|undefined}
+   */
+  this.currentTarget = null;
+
+  /**
+   * For mouseover and mouseout events, the related object for the event.
+   * @type {?Node}
+   */
+  this.relatedTarget = null;
+
+  /**
+   * X-coordinate relative to target.
+   * @type {number}
+   */
+  this.offsetX = 0;
+
+  /**
+   * Y-coordinate relative to target.
+   * @type {number}
+   */
+  this.offsetY = 0;
+
+  /**
+   * X-coordinate relative to the window.
+   * @type {number}
+   */
+  this.clientX = 0;
+
+  /**
+   * Y-coordinate relative to the window.
+   * @type {number}
+   */
+  this.clientY = 0;
+
+  /**
+   * X-coordinate relative to the monitor.
+   * @type {number}
+   */
+  this.screenX = 0;
+
+  /**
+   * Y-coordinate relative to the monitor.
+   * @type {number}
+   */
+  this.screenY = 0;
+
+  /**
+   * Which mouse button was pressed.
+   * @type {number}
+   */
+  this.button = 0;
+
+  /**
+   * Key of key press.
+   * @type {string}
+   */
+  this.key = '';
+
+  /**
+   * Keycode of key press.
+   * @type {number}
+   */
+  this.keyCode = 0;
+
+  /**
+   * Keycode of key press.
+   * @type {number}
+   */
+  this.charCode = 0;
+
+  /**
+   * Whether control was pressed at time of event.
+   * @type {boolean}
+   */
+  this.ctrlKey = false;
+
+  /**
+   * Whether alt was pressed at time of event.
+   * @type {boolean}
+   */
+  this.altKey = false;
+
+  /**
+   * Whether shift was pressed at time of event.
+   * @type {boolean}
+   */
+  this.shiftKey = false;
+
+  /**
+   * Whether the meta key was pressed at time of event.
+   * @type {boolean}
+   */
+  this.metaKey = false;
+
+  /**
+   * History state object, only set for PopState events where it's a copy of the
+   * state object provided to pushState or replaceState.
+   * @type {?Object}
+   */
+  this.state = null;
+
+  /**
+   * Whether the default platform modifier key was pressed at time of event.
+   * (This is control for all platforms except Mac, where it's Meta.)
+   * @type {boolean}
+   */
+  this.platformModifierKey = false;
+
+  /**
+   * @type {number}
+   */
+  this.pointerId = 0;
+
+  /**
+   * @type {string}
+   */
+  this.pointerType = '';
+
+  /**
+   * The browser event object.
+   * @private {?Event}
+   */
+  this.event_ = null;
+
+  if (opt_e) {
+    this.init(opt_e, opt_currentTarget);
+  }
+};
+goog.inherits(goog.events.BrowserEvent, goog.events.Event);
+
+
+/**
+ * Normalized button constants for the mouse.
+ * @enum {number}
+ */
+goog.events.BrowserEvent.MouseButton = {
+  LEFT: 0,
+  MIDDLE: 1,
+  RIGHT: 2
+};
+
+
+/**
+ * Normalized pointer type constants for pointer events.
+ * @enum {string}
+ */
+goog.events.BrowserEvent.PointerType = {
+  MOUSE: 'mouse',
+  PEN: 'pen',
+  TOUCH: 'touch'
+};
+
+
+/**
+ * Static data for mapping mouse buttons.
+ * @type {!Array<number>}
+ * @deprecated Use `goog.events.BrowserEvent.IE_BUTTON_MAP` instead.
+ */
+goog.events.BrowserEvent.IEButtonMap = goog.debug.freeze([
+  1,  // LEFT
+  4,  // MIDDLE
+  2   // RIGHT
+]);
+
+
+/**
+ * Static data for mapping mouse buttons.
+ * @const {!Array<number>}
+ */
+goog.events.BrowserEvent.IE_BUTTON_MAP = goog.events.BrowserEvent.IEButtonMap;
+
+
+/**
+ * Static data for mapping MSPointerEvent types to PointerEvent types.
+ * @const {!Object<number, goog.events.BrowserEvent.PointerType>}
+ */
+goog.events.BrowserEvent.IE_POINTER_TYPE_MAP = goog.debug.freeze({
+  2: goog.events.BrowserEvent.PointerType.TOUCH,
+  3: goog.events.BrowserEvent.PointerType.PEN,
+  4: goog.events.BrowserEvent.PointerType.MOUSE
+});
+
+
+/**
+ * Accepts a browser event object and creates a patched, cross browser event
+ * object.
+ * @param {Event} e Browser event object.
+ * @param {EventTarget=} opt_currentTarget Current target for event.
+ */
+goog.events.BrowserEvent.prototype.init = function(e, opt_currentTarget) {
+  'use strict';
+  var type = this.type = e.type;
+
+  /**
+   * On touch devices use the first "changed touch" as the relevant touch.
+   * @type {?Touch}
+   */
+  var relevantTouch =
+      e.changedTouches && e.changedTouches.length ? e.changedTouches[0] : null;
+
+  // TODO(nicksantos): Change this.target to type EventTarget.
+  this.target = /** @type {Node} */ (e.target) || e.srcElement;
+
+  // TODO(nicksantos): Change this.currentTarget to type EventTarget.
+  this.currentTarget = /** @type {Node} */ (opt_currentTarget);
+
+  var relatedTarget = /** @type {Node} */ (e.relatedTarget);
+  if (relatedTarget) {
+    // There's a bug in FireFox where sometimes, relatedTarget will be a
+    // chrome element, and accessing any property of it will get a permission
+    // denied exception. See:
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=497780
+    if (goog.userAgent.GECKO) {
+      if (!goog.reflect.canAccessProperty(relatedTarget, 'nodeName')) {
+        relatedTarget = null;
+      }
+    }
+  } else if (type == goog.events.EventType.MOUSEOVER) {
+    relatedTarget = e.fromElement;
+  } else if (type == goog.events.EventType.MOUSEOUT) {
+    relatedTarget = e.toElement;
+  }
+
+  this.relatedTarget = relatedTarget;
+
+  if (relevantTouch) {
+    this.clientX = relevantTouch.clientX !== undefined ? relevantTouch.clientX :
+                                                         relevantTouch.pageX;
+    this.clientY = relevantTouch.clientY !== undefined ? relevantTouch.clientY :
+                                                         relevantTouch.pageY;
+    this.screenX = relevantTouch.screenX || 0;
+    this.screenY = relevantTouch.screenY || 0;
+  } else {
+    if (goog.events.USE_LAYER_XY_AS_OFFSET_XY) {
+      this.offsetX = (e.layerX !== undefined) ? e.layerX : e.offsetX;
+      this.offsetY = (e.layerY !== undefined) ? e.layerY : e.offsetY;
+    } else {
+      // Webkit emits a lame warning whenever layerX/layerY is accessed.
+      // http://code.google.com/p/chromium/issues/detail?id=101733
+      this.offsetX = (goog.userAgent.WEBKIT || e.offsetX !== undefined) ?
+          e.offsetX :
+          e.layerX;
+      this.offsetY = (goog.userAgent.WEBKIT || e.offsetY !== undefined) ?
+          e.offsetY :
+          e.layerY;
+    }
+    this.clientX = e.clientX !== undefined ? e.clientX : e.pageX;
+    this.clientY = e.clientY !== undefined ? e.clientY : e.pageY;
+    this.screenX = e.screenX || 0;
+    this.screenY = e.screenY || 0;
+  }
+
+  this.button = e.button;
+
+  this.keyCode = e.keyCode || 0;
+  this.key = e.key || '';
+  this.charCode = e.charCode || (type == 'keypress' ? e.keyCode : 0);
+  this.ctrlKey = e.ctrlKey;
+  this.altKey = e.altKey;
+  this.shiftKey = e.shiftKey;
+  this.metaKey = e.metaKey;
+  this.platformModifierKey = goog.userAgent.MAC ? e.metaKey : e.ctrlKey;
+  this.pointerId = e.pointerId || 0;
+  this.pointerType = goog.events.BrowserEvent.getPointerType_(e);
+  this.state = e.state;
+  this.event_ = e;
+  if (e.defaultPrevented) {
+    // Sync native event state to internal state via super class, where default
+    // prevention is implemented and managed.
+    goog.events.BrowserEvent.superClass_.preventDefault.call(this);
+  }
+};
+
+
+/**
+ * Tests to see which button was pressed during the event. This is really only
+ * useful in IE and Gecko browsers. And in IE, it's only useful for
+ * mousedown/mouseup events, because click only fires for the left mouse button.
+ *
+ * Safari 2 only reports the left button being clicked, and uses the value '1'
+ * instead of 0. Opera only reports a mousedown event for the middle button, and
+ * no mouse events for the right button. Opera has default behavior for left and
+ * middle click that can only be overridden via a configuration setting.
+ *
+ * There's a nice table of this mess at http://www.unixpapa.com/js/mouse.html.
+ *
+ * @param {goog.events.BrowserEvent.MouseButton} button The button
+ *     to test for.
+ * @return {boolean} True if button was pressed.
+ */
+goog.events.BrowserEvent.prototype.isButton = function(button) {
+  'use strict';
+  return this.event_.button == button;
+};
+
+
+/**
+ * Whether this has an "action"-producing mouse button.
+ *
+ * By definition, this includes left-click on windows/linux, and left-click
+ * without the ctrl key on Macs.
+ *
+ * @return {boolean} The result.
+ */
+goog.events.BrowserEvent.prototype.isMouseActionButton = function() {
+  'use strict';
+  // Ctrl+click should never behave like a left-click on mac, regardless of
+  // whether or not the browser will actually ever emit such an event.  If
+  // we see it, treat it like right-click always.
+  return this.isButton(goog.events.BrowserEvent.MouseButton.LEFT) &&
+      !(goog.userAgent.MAC && this.ctrlKey);
+};
+
+
+/**
+ * @override
+ */
+goog.events.BrowserEvent.prototype.stopPropagation = function() {
+  'use strict';
+  goog.events.BrowserEvent.superClass_.stopPropagation.call(this);
+  if (this.event_.stopPropagation) {
+    this.event_.stopPropagation();
+  } else {
+    this.event_.cancelBubble = true;
+  }
+};
+
+
+/**
+ * @override
+ */
+goog.events.BrowserEvent.prototype.preventDefault = function() {
+  'use strict';
+  goog.events.BrowserEvent.superClass_.preventDefault.call(this);
+  var be = this.event_;
+  if (!be.preventDefault) {
+    be.returnValue = false;
+  } else {
+    be.preventDefault();
+  }
+};
+
+
+/**
+ * @return {Event} The underlying browser event object.
+ */
+goog.events.BrowserEvent.prototype.getBrowserEvent = function() {
+  'use strict';
+  return this.event_;
+};
+
+
+/**
+ * Extracts the pointer type from the given event.
+ * @param {!Event} e
+ * @return {string} The pointer type, e.g. 'mouse', 'pen', or 'touch'.
+ * @private
+ */
+goog.events.BrowserEvent.getPointerType_ = function(e) {
+  'use strict';
+  if (typeof (e.pointerType) === 'string') {
+    return e.pointerType;
+  }
+  // IE10 uses integer codes for pointer type.
+  // https://msdn.microsoft.com/en-us/library/hh772359(v=vs.85).aspx
+  return goog.events.BrowserEvent.IE_POINTER_TYPE_MAP[e.pointerType] || '';
+};

js/goog/events/browserfeature.js

@@ -0,0 +1,118 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Browser capability checks for the events package.
+ */
+
+goog.module('goog.events.BrowserFeature');
+goog.module.declareLegacyNamespace();
+
+
+/**
+ * Tricks Closure Compiler into believing that a function is pure.  The compiler
+ * assumes that any `valueOf` function is pure, without analyzing its contents.
+ *
+ * @param {function(): T} fn
+ * @return {T}
+ * @template T
+ */
+const purify = (fn) => {
+  return ({valueOf: fn}).valueOf();
+};
+
+
+/**
+ * Enum of browser capabilities.
+ * @enum {boolean}
+ */
+exports = {
+  /**
+   * Whether the button attribute of the event is W3C compliant.  False in
+   * Internet Explorer prior to version 9; document-version dependent.
+   */
+  HAS_W3C_BUTTON: true,
+
+  /**
+   * Whether the browser supports full W3C event model.
+   */
+  HAS_W3C_EVENT_SUPPORT: true,
+
+  /**
+   * To prevent default in IE7-8 for certain keydown events we need set the
+   * keyCode to -1.
+   */
+  SET_KEY_CODE_TO_PREVENT_DEFAULT: false,
+
+  /**
+   * Whether the `navigator.onLine` property is supported.
+   */
+  HAS_NAVIGATOR_ONLINE_PROPERTY: true,
+
+  /**
+   * Whether HTML5 network online/offline events are supported.
+   */
+  HAS_HTML5_NETWORK_EVENT_SUPPORT: true,
+
+  /**
+   * Whether HTML5 network events fire on document.body, or otherwise the
+   * window.
+   */
+  HTML5_NETWORK_EVENTS_FIRE_ON_BODY: false,
+
+  /**
+   * Whether touch is enabled in the browser.
+   */
+  TOUCH_ENABLED:
+      ('ontouchstart' in goog.global ||
+       !!(goog.global['document'] && document.documentElement &&
+          'ontouchstart' in document.documentElement) ||
+       // IE10 uses non-standard touch events, so it has a different check.
+       !!(goog.global['navigator'] &&
+          (goog.global['navigator']['maxTouchPoints'] ||
+           goog.global['navigator']['msMaxTouchPoints']))),
+
+  /**
+   * Whether addEventListener supports W3C standard pointer events.
+   * http://www.w3.org/TR/pointerevents/
+   */
+  POINTER_EVENTS: ('PointerEvent' in goog.global),
+
+  /**
+   * Whether addEventListener supports MSPointer events (only used in IE10).
+   * http://msdn.microsoft.com/en-us/library/ie/hh772103(v=vs.85).aspx
+   * http://msdn.microsoft.com/library/hh673557(v=vs.85).aspx
+   */
+  MSPOINTER_EVENTS:
+      ('MSPointerEvent' in goog.global &&
+       !!(goog.global['navigator'] &&
+          goog.global['navigator']['msPointerEnabled'])),
+
+  /**
+   * Whether addEventListener supports {passive: true}.
+   * https://developers.google.com/web/updates/2016/06/passive-event-listeners
+   */
+  PASSIVE_EVENTS: purify(function() {
+    // If we're in a web worker or other custom environment, we can't tell.
+    if (!goog.global.addEventListener || !Object.defineProperty) {  // IE 8
+      return false;
+    }
+
+    var passive = false;
+    var options = Object.defineProperty({}, 'passive', {
+      get: function() {
+        passive = true;
+      }
+    });
+    try {
+      goog.global.addEventListener('test', goog.nullFunction, options);
+      goog.global.removeEventListener('test', goog.nullFunction, options);
+    } catch (e) {
+    }
+
+    return passive;
+  })
+};

js/goog/events/event.js

@@ -0,0 +1,125 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A base class for event objects.
+ */
+
+
+goog.provide('goog.events.Event');
+
+/**
+ * goog.events.Event no longer depends on goog.Disposable. Keep requiring
+ * goog.Disposable here to not break projects which assume this dependency.
+ * @suppress {extraRequire}
+ */
+goog.require('goog.Disposable');
+goog.require('goog.events.EventId');
+
+
+/**
+ * A base class for event objects, so that they can support preventDefault and
+ * stopPropagation.
+ *
+ * @param {string|!goog.events.EventId} type Event Type.
+ * @param {Object=} opt_target Reference to the object that is the target of
+ *     this event. It has to implement the `EventTarget` interface
+ *     declared at {@link http://developer.mozilla.org/en/DOM/EventTarget}.
+ * @constructor
+ */
+goog.events.Event = function(type, opt_target) {
+  'use strict';
+  /**
+   * Event type.
+   * @type {string}
+   */
+  this.type = type instanceof goog.events.EventId ? String(type) : type;
+
+  /**
+   * TODO(tbreisacher): The type should probably be
+   * EventTarget|goog.events.EventTarget.
+   *
+   * Target of the event.
+   * @type {Object|undefined}
+   */
+  this.target = opt_target;
+
+  /**
+   * Object that had the listener attached.
+   * @type {Object|undefined}
+   */
+  this.currentTarget = this.target;
+
+  /**
+   * Whether to cancel the event in internal capture/bubble processing for IE.
+   * @type {boolean}
+   * @private
+   */
+  this.propagationStopped_ = false;
+
+  /**
+   * Whether the default action has been prevented.
+   * This is a property to match the W3C specification at
+   * {@link http://www.w3.org/TR/DOM-Level-3-Events/
+   * #events-event-type-defaultPrevented}.
+   * Must be treated as read-only outside the class.
+   * @type {boolean}
+   */
+  this.defaultPrevented = false;
+};
+
+/**
+ * @return {boolean} true iff internal propagation has been stopped.
+ */
+goog.events.Event.prototype.hasPropagationStopped = function() {
+  'use strict';
+  return this.propagationStopped_;
+};
+
+/**
+ * Stops event propagation.
+ * @return {void}
+ */
+goog.events.Event.prototype.stopPropagation = function() {
+  'use strict';
+  this.propagationStopped_ = true;
+};
+
+
+/**
+ * Prevents the default action, for example a link redirecting to a url.
+ * @return {void}
+ */
+goog.events.Event.prototype.preventDefault = function() {
+  'use strict';
+  this.defaultPrevented = true;
+};
+
+
+/**
+ * Stops the propagation of the event. It is equivalent to
+ * `e.stopPropagation()`, but can be used as the callback argument of
+ * {@link goog.events.listen} without declaring another function.
+ * @param {!goog.events.Event} e An event.
+ * @return {void}
+ */
+goog.events.Event.stopPropagation = function(e) {
+  'use strict';
+  e.stopPropagation();
+};
+
+
+/**
+ * Prevents the default action. It is equivalent to
+ * `e.preventDefault()`, but can be used as the callback argument of
+ * {@link goog.events.listen} without declaring another function.
+ * @param {!goog.events.Event} e An event.
+ * @return {void}
+ */
+goog.events.Event.preventDefault = function(e) {
+  'use strict';
+  e.preventDefault();
+};

js/goog/events/eventhandler.js

@@ -0,0 +1,488 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Class to create objects which want to handle multiple events
+ * and have their listeners easily cleaned up via a dispose method.
+ *
+ * Example:
+ * <pre>
+ * function Something() {
+ *   Something.base(this);
+ *
+ *   ... set up object ...
+ *
+ *   // Add event listeners
+ *   this.listen(this.starEl, goog.events.EventType.CLICK, this.handleStar);
+ *   this.listen(this.headerEl, goog.events.EventType.CLICK, this.expand);
+ *   this.listen(this.collapseEl, goog.events.EventType.CLICK, this.collapse);
+ *   this.listen(this.infoEl, goog.events.EventType.MOUSEOVER, this.showHover);
+ *   this.listen(this.infoEl, goog.events.EventType.MOUSEOUT, this.hideHover);
+ * }
+ * goog.inherits(Something, goog.events.EventHandler);
+ *
+ * Something.prototype.disposeInternal = function() {
+ *   Something.base(this, 'disposeInternal');
+ *   goog.dom.removeNode(this.container);
+ * };
+ *
+ *
+ * // Then elsewhere:
+ *
+ * var activeSomething = null;
+ * function openSomething() {
+ *   activeSomething = new Something();
+ * }
+ *
+ * function closeSomething() {
+ *   if (activeSomething) {
+ *     activeSomething.dispose();  // Remove event listeners
+ *     activeSomething = null;
+ *   }
+ * }
+ * </pre>
+ */
+
+goog.provide('goog.events.EventHandler');
+
+goog.require('goog.Disposable');
+goog.require('goog.events');
+goog.require('goog.object');
+goog.requireType('goog.events.Event');
+goog.requireType('goog.events.EventId');
+goog.requireType('goog.events.EventTarget');
+goog.requireType('goog.events.EventWrapper');
+
+
+
+/**
+ * Super class for objects that want to easily manage a number of event
+ * listeners.  It allows a short cut to listen and also provides a quick way
+ * to remove all events listeners belonging to this object.
+ * @param {SCOPE=} opt_scope Object in whose scope to call the listeners.
+ * @constructor
+ * @extends {goog.Disposable}
+ * @template SCOPE
+ */
+goog.events.EventHandler = function(opt_scope) {
+  'use strict';
+  goog.Disposable.call(this);
+  // TODO(mknichel): Rename this to this.scope_ and fix the classes in google3
+  // that access this private variable. :(
+  this.handler_ = opt_scope;
+
+  /**
+   * Keys for events that are being listened to.
+   * @type {!Object<!goog.events.Key>}
+   * @private
+   */
+  this.keys_ = {};
+};
+goog.inherits(goog.events.EventHandler, goog.Disposable);
+
+
+/**
+ * Utility array used to unify the cases of listening for an array of types
+ * and listening for a single event, without using recursion or allocating
+ * an array each time.
+ * @type {!Array<string>}
+ * @const
+ * @private
+ */
+goog.events.EventHandler.typeArray_ = [];
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted then the
+ * EventHandler's handleEvent method will be used.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(this:SCOPE, EVENTOBJ):?|{handleEvent:function(?):?}|null=}
+ *     opt_fn Optional callback function to be used as the listener or an object
+ *     with handleEvent function.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template EVENTOBJ, THIS
+ */
+goog.events.EventHandler.prototype.listen = function(
+    src, type, opt_fn, opt_options) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  return self.listen_(src, type, opt_fn, opt_options);
+};
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted then the
+ * EventHandler's handleEvent method will be used.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(this:T, EVENTOBJ):?|{handleEvent:function(this:T, ?):?}|
+ *     null|undefined} fn Optional callback function to be used as the
+ *     listener or an object with handleEvent function.
+ * @param {boolean|!AddEventListenerOptions|undefined} options
+ * @param {T} scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template T, EVENTOBJ, THIS
+ */
+goog.events.EventHandler.prototype.listenWithScope = function(
+    src, type, fn, options, scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  // TODO(mknichel): Deprecate this function.
+  return self.listen_(src, type, fn, options, scope);
+};
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted then the
+ * EventHandler's handleEvent method will be used.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(EVENTOBJ):?|{handleEvent:function(?):?}|null=} opt_fn
+ *     Optional callback function to be used as the listener or an object with
+ *     handleEvent function.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @param {Object=} opt_scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template EVENTOBJ, THIS
+ * @private
+ */
+goog.events.EventHandler.prototype.listen_ = function(
+    src, type, opt_fn, opt_options, opt_scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  if (!Array.isArray(type)) {
+    if (type) {
+      goog.events.EventHandler.typeArray_[0] = type.toString();
+    }
+    type = goog.events.EventHandler.typeArray_;
+  }
+  for (var i = 0; i < type.length; i++) {
+    var listenerObj = goog.events.listen(
+        src, type[i], opt_fn || self.handleEvent, opt_options || false,
+        opt_scope || self.handler_ || self);
+
+    if (!listenerObj) {
+      // When goog.events.listen run on OFF_AND_FAIL or OFF_AND_SILENT
+      // (goog.events.CaptureSimulationMode) in IE8-, it will return null
+      // value.
+      return self;
+    }
+
+    var key = listenerObj.key;
+    self.keys_[key] = listenerObj;
+  }
+
+  return self;
+};
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted, then the
+ * EventHandler's handleEvent method will be used. After the event has fired the
+ * event listener is removed from the target. If an array of event types is
+ * provided, each event type will be listened to once.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(this:SCOPE, EVENTOBJ):?|{handleEvent:function(?):?}|null=}
+ * opt_fn
+ *    Optional callback function to be used as the listener or an object with
+ *    handleEvent function.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template EVENTOBJ, THIS
+ */
+goog.events.EventHandler.prototype.listenOnce = function(
+    src, type, opt_fn, opt_options) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  return self.listenOnce_(src, type, opt_fn, opt_options);
+};
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted, then the
+ * EventHandler's handleEvent method will be used. After the event has fired the
+ * event listener is removed from the target. If an array of event types is
+ * provided, each event type will be listened to once.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(this:T, EVENTOBJ):?|{handleEvent:function(this:T, ?):?}|
+ *     null|undefined} fn Optional callback function to be used as the
+ *     listener or an object with handleEvent function.
+ * @param {boolean|undefined} capture Optional whether to use capture phase.
+ * @param {T} scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template T, EVENTOBJ, THIS
+ */
+goog.events.EventHandler.prototype.listenOnceWithScope = function(
+    src, type, fn, capture, scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  // TODO(mknichel): Deprecate this function.
+  return self.listenOnce_(src, type, fn, capture, scope);
+};
+
+
+/**
+ * Listen to an event on a Listenable.  If the function is omitted, then the
+ * EventHandler's handleEvent method will be used. After the event has fired
+ * the event listener is removed from the target. If an array of event types is
+ * provided, each event type will be listened to once.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type to listen for or array of event types.
+ * @param {function(EVENTOBJ):?|{handleEvent:function(?):?}|null=} opt_fn
+ *    Optional callback function to be used as the listener or an object with
+ *    handleEvent function.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @param {Object=} opt_scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template EVENTOBJ, THIS
+ * @private
+ */
+goog.events.EventHandler.prototype.listenOnce_ = function(
+    src, type, opt_fn, opt_options, opt_scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  if (Array.isArray(type)) {
+    for (var i = 0; i < type.length; i++) {
+      self.listenOnce_(src, type[i], opt_fn, opt_options, opt_scope);
+    }
+  } else {
+    var listenerObj = goog.events.listenOnce(
+        src, type, opt_fn || self.handleEvent, opt_options,
+        opt_scope || self.handler_ || self);
+    if (!listenerObj) {
+      // When goog.events.listen run on OFF_AND_FAIL or OFF_AND_SILENT
+      // (goog.events.CaptureSimulationMode) in IE8-, it will return null
+      // value.
+      return self;
+    }
+
+    var key = listenerObj.key;
+    self.keys_[key] = listenerObj;
+  }
+
+  return self;
+};
+
+
+/**
+ * Adds an event listener with a specific event wrapper on a DOM Node or an
+ * object that has implemented {@link goog.events.EventTarget}. A listener can
+ * only be added once to an object.
+ *
+ * @param {EventTarget|goog.events.EventTarget} src The node to listen to
+ *     events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(this:SCOPE, ?):?|{handleEvent:function(?):?}|null} listener
+ *     Callback method, or an object with a handleEvent function.
+ * @param {boolean=} opt_capt Whether to fire in capture phase (defaults to
+ *     false).
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template THIS
+ */
+goog.events.EventHandler.prototype.listenWithWrapper = function(
+    src, wrapper, listener, opt_capt) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  // TODO(mknichel): Remove the opt_scope from this function and then
+  // templatize it.
+  return self.listenWithWrapper_(src, wrapper, listener, opt_capt);
+};
+
+
+/**
+ * Adds an event listener with a specific event wrapper on a DOM Node or an
+ * object that has implemented {@link goog.events.EventTarget}. A listener can
+ * only be added once to an object.
+ *
+ * @param {EventTarget|goog.events.EventTarget} src The node to listen to
+ *     events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(this:T, ?):?|{handleEvent:function(this:T, ?):?}|null}
+ *     listener Optional callback function to be used as the
+ *     listener or an object with handleEvent function.
+ * @param {boolean|undefined} capture Optional whether to use capture phase.
+ * @param {T} scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template T, THIS
+ */
+goog.events.EventHandler.prototype.listenWithWrapperAndScope = function(
+    src, wrapper, listener, capture, scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  // TODO(mknichel): Deprecate this function.
+  return self.listenWithWrapper_(src, wrapper, listener, capture, scope);
+};
+
+
+/**
+ * Adds an event listener with a specific event wrapper on a DOM Node or an
+ * object that has implemented {@link goog.events.EventTarget}. A listener can
+ * only be added once to an object.
+ *
+ * @param {EventTarget|goog.events.EventTarget} src The node to listen to
+ *     events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener Callback
+ *     method, or an object with a handleEvent function.
+ * @param {boolean=} opt_capt Whether to fire in capture phase (defaults to
+ *     false).
+ * @param {Object=} opt_scope Element in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template THIS
+ * @private
+ */
+goog.events.EventHandler.prototype.listenWithWrapper_ = function(
+    src, wrapper, listener, opt_capt, opt_scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  wrapper.listen(
+      src, listener, opt_capt, opt_scope || self.handler_ || self, self);
+  return self;
+};
+
+
+/**
+ * @return {number} Number of listeners registered by this handler.
+ */
+goog.events.EventHandler.prototype.getListenerCount = function() {
+  'use strict';
+  var count = 0;
+  for (var key in this.keys_) {
+    if (Object.prototype.hasOwnProperty.call(this.keys_, key)) {
+      count++;
+    }
+  }
+  return count;
+};
+
+
+/**
+ * Unlistens on an event.
+ * @param {goog.events.ListenableType} src Event source.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type or array of event types to unlisten to.
+ * @param {function(this:?, EVENTOBJ):?|{handleEvent:function(?):?}|null=}
+ *     opt_fn Optional callback function to be used as the listener or an object
+ *     with handleEvent function.
+ * @param {(boolean|!EventListenerOptions)=} opt_options
+ * @param {Object=} opt_scope Object in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template EVENTOBJ, THIS
+ */
+goog.events.EventHandler.prototype.unlisten = function(
+    src, type, opt_fn, opt_options, opt_scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  if (Array.isArray(type)) {
+    for (var i = 0; i < type.length; i++) {
+      self.unlisten(src, type[i], opt_fn, opt_options, opt_scope);
+    }
+  } else {
+    var capture =
+        goog.isObject(opt_options) ? !!opt_options.capture : !!opt_options;
+    var listener = goog.events.getListener(
+        src, type, opt_fn || self.handleEvent, capture,
+        opt_scope || self.handler_ || self);
+
+    if (listener) {
+      goog.events.unlistenByKey(listener);
+      delete self.keys_[listener.key];
+    }
+  }
+
+  return self;
+};
+
+
+/**
+ * Removes an event listener which was added with listenWithWrapper().
+ *
+ * @param {EventTarget|goog.events.EventTarget} src The target to stop
+ *     listening to events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener The
+ *     listener function to remove.
+ * @param {boolean=} opt_capt In DOM-compliant browsers, this determines
+ *     whether the listener is fired during the capture or bubble phase of the
+ *     event.
+ * @param {Object=} opt_scope Element in whose scope to call the listener.
+ * @return {THIS} This object, allowing for chaining of calls.
+ * @this {THIS}
+ * @template THIS
+ */
+goog.events.EventHandler.prototype.unlistenWithWrapper = function(
+    src, wrapper, listener, opt_capt, opt_scope) {
+  'use strict';
+  var self = /** @type {!goog.events.EventHandler} */ (this);
+  wrapper.unlisten(
+      src, listener, opt_capt, opt_scope || self.handler_ || self, self);
+  return self;
+};
+
+
+/**
+ * Unlistens to all events.
+ */
+goog.events.EventHandler.prototype.removeAll = function() {
+  'use strict';
+  goog.object.forEach(this.keys_, function(listenerObj, key) {
+    'use strict';
+    if (this.keys_.hasOwnProperty(key)) {
+      goog.events.unlistenByKey(listenerObj);
+    }
+  }, this);
+
+  this.keys_ = {};
+};
+
+
+/**
+ * Disposes of this EventHandler and removes all listeners that it registered.
+ * @override
+ * @protected
+ */
+goog.events.EventHandler.prototype.disposeInternal = function() {
+  'use strict';
+  goog.events.EventHandler.superClass_.disposeInternal.call(this);
+  this.removeAll();
+};
+
+
+/**
+ * Default event handler
+ * @param {goog.events.Event} e Event object.
+ */
+goog.events.EventHandler.prototype.handleEvent = function(e) {
+  'use strict';
+  throw new Error('EventHandler.handleEvent not implemented');
+};

js/goog/events/eventid.js

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.provide('goog.events.EventId');
+
+
+
+/**
+ * A templated class that is used when registering for events. Typical usage:
+ *
+ *    /** @type {goog.events.EventId<MyEventObj>} *\
+ *    var myEventId = new goog.events.EventId(
+ *        goog.events.getUniqueId(('someEvent'));
+ *
+ *    // No need to cast or declare here since the compiler knows the
+ *    // correct type of 'evt' (MyEventObj).
+ *    something.listen(myEventId, function(evt) {});
+ *
+ * @param {string} eventId
+ * @template T
+ * @constructor
+ * @struct
+ * @final
+ */
+goog.events.EventId = function(eventId) {
+  'use strict';
+  /** @const */ this.id = eventId;
+};
+
+
+/**
+ * @override
+ * @return {string}
+ */
+goog.events.EventId.prototype.toString = function() {
+  'use strict';
+  return this.id;
+};

js/goog/events/eventlike.js

@@ -0,0 +1,24 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A typedef for event like objects that are dispatchable via the
+ * goog.events.dispatchEvent function.
+ */
+goog.provide('goog.events.EventLike');
+
+goog.requireType('goog.events.Event');
+goog.requireType('goog.events.EventId');
+
+/**
+ * A typedef for event like objects that are dispatchable via the
+ * goog.events.dispatchEvent function. strings are treated as the type for a
+ * goog.events.Event. Objects are treated as an extension of a new
+ * goog.events.Event with the type property of the object being used as the type
+ * of the Event.
+ * @typedef {string|Object|goog.events.Event|goog.events.EventId}
+ */
+goog.events.EventLike;

js/goog/events/events.js

@@ -0,0 +1,960 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview An event manager for both native browser event
+ * targets and custom JavaScript event targets
+ * (`goog.events.Listenable`). This provides an abstraction
+ * over browsers' event systems.
+ *
+ * It also provides a simulation of W3C event model's capture phase in
+ * Internet Explorer (IE 8 and below). Caveat: the simulation does not
+ * interact well with listeners registered directly on the elements
+ * (bypassing goog.events) or even with listeners registered via
+ * goog.events in a separate JS binary. In these cases, we provide
+ * no ordering guarantees.
+ *
+ * The listeners will receive a "patched" event object. Such event object
+ * contains normalized values for certain event properties that differs in
+ * different browsers.
+ *
+ * Example usage:
+ * <pre>
+ * goog.events.listen(myNode, 'click', function(e) { alert('woo') });
+ * goog.events.listen(myNode, 'mouseover', mouseHandler, true);
+ * goog.events.unlisten(myNode, 'mouseover', mouseHandler, true);
+ * goog.events.removeAll(myNode);
+ * </pre>
+ *
+ *                                            in IE and event object patching]
+ *
+ * @see ../demos/events.html
+ * @see ../demos/event-propagation.html
+ * @see ../demos/stopevent.html
+ */
+
+// IMPLEMENTATION NOTES:
+// goog.events stores an auxiliary data structure on each EventTarget
+// source being listened on. This allows us to take advantage of GC,
+// having the data structure GC'd when the EventTarget is GC'd. This
+// GC behavior is equivalent to using W3C DOM Events directly.
+
+goog.provide('goog.events');
+goog.provide('goog.events.CaptureSimulationMode');
+goog.provide('goog.events.Key');
+goog.provide('goog.events.ListenableType');
+
+goog.require('goog.asserts');
+goog.require('goog.debug.entryPointRegistry');
+goog.require('goog.events.BrowserEvent');
+goog.require('goog.events.BrowserFeature');
+goog.require('goog.events.Listenable');
+goog.require('goog.events.ListenerMap');
+goog.requireType('goog.debug.ErrorHandler');
+goog.requireType('goog.events.EventId');
+goog.requireType('goog.events.EventLike');
+goog.requireType('goog.events.EventWrapper');
+goog.requireType('goog.events.ListenableKey');
+goog.requireType('goog.events.Listener');
+
+
+/**
+ * @typedef {number|goog.events.ListenableKey}
+ */
+goog.events.Key;
+
+
+/**
+ * @typedef {EventTarget|goog.events.Listenable}
+ */
+goog.events.ListenableType;
+
+
+/**
+ * Property name on a native event target for the listener map
+ * associated with the event target.
+ * @private @const {string}
+ */
+goog.events.LISTENER_MAP_PROP_ = 'closure_lm_' + ((Math.random() * 1e6) | 0);
+
+
+/**
+ * String used to prepend to IE event types.
+ * @const
+ * @private
+ */
+goog.events.onString_ = 'on';
+
+
+/**
+ * Map of computed "on<eventname>" strings for IE event types. Caching
+ * this removes an extra object allocation in goog.events.listen which
+ * improves IE6 performance.
+ * @const
+ * @dict
+ * @private
+ */
+goog.events.onStringMap_ = {};
+
+
+/**
+ * @enum {number} Different capture simulation mode for IE8-.
+ */
+goog.events.CaptureSimulationMode = {
+  /**
+   * Does not perform capture simulation. Will asserts in IE8- when you
+   * add capture listeners.
+   */
+  OFF_AND_FAIL: 0,
+
+  /**
+   * Does not perform capture simulation, silently ignore capture
+   * listeners.
+   */
+  OFF_AND_SILENT: 1,
+
+  /**
+   * Performs capture simulation.
+   */
+  ON: 2
+};
+
+
+/**
+ * @define {number} The capture simulation mode for IE8-. By default,
+ *     this is ON.
+ */
+goog.events.CAPTURE_SIMULATION_MODE =
+    goog.define('goog.events.CAPTURE_SIMULATION_MODE', 2);
+
+
+/**
+ * Estimated count of total native listeners.
+ * @private {number}
+ */
+goog.events.listenerCountEstimate_ = 0;
+
+
+/**
+ * Adds an event listener for a specific event on a native event
+ * target (such as a DOM element) or an object that has implemented
+ * {@link goog.events.Listenable}. A listener can only be added once
+ * to an object and if it is added again the key for the listener is
+ * returned. Note that if the existing listener is a one-off listener
+ * (registered via listenOnce), it will no longer be a one-off
+ * listener after a call to listen().
+ *
+ * @param {EventTarget|goog.events.Listenable} src The node to listen
+ *     to events on.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type or array of event types.
+ * @param {function(this:T, EVENTOBJ):?|{handleEvent:function(?):?}|null}
+ *     listener Callback method, or an object with a handleEvent function.
+ *     WARNING: passing an Object is now softly deprecated.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @param {T=} opt_handler Element in whose scope to call the listener.
+ * @return {goog.events.Key} Unique key for the listener.
+ * @template T,EVENTOBJ
+ */
+goog.events.listen = function(src, type, listener, opt_options, opt_handler) {
+  'use strict';
+  if (opt_options && opt_options.once) {
+    return goog.events.listenOnce(
+        src, type, listener, opt_options, opt_handler);
+  }
+  if (Array.isArray(type)) {
+    for (var i = 0; i < type.length; i++) {
+      goog.events.listen(src, type[i], listener, opt_options, opt_handler);
+    }
+    return null;
+  }
+
+  listener = goog.events.wrapListener(listener);
+  if (goog.events.Listenable.isImplementedBy(src)) {
+    var capture =
+        goog.isObject(opt_options) ? !!opt_options.capture : !!opt_options;
+    return src.listen(
+        /** @type {string|!goog.events.EventId} */ (type), listener, capture,
+        opt_handler);
+  } else {
+    return goog.events.listen_(
+        /** @type {!EventTarget} */ (src), type, listener,
+        /* callOnce */ false, opt_options, opt_handler);
+  }
+};
+
+
+/**
+ * Adds an event listener for a specific event on a native event
+ * target. A listener can only be added once to an object and if it
+ * is added again the key for the listener is returned.
+ *
+ * Note that a one-off listener will not change an existing listener,
+ * if any. On the other hand a normal listener will change existing
+ * one-off listener to become a normal listener.
+ *
+ * @param {EventTarget} src The node to listen to events on.
+ * @param {string|?goog.events.EventId<EVENTOBJ>} type Event type.
+ * @param {!Function} listener Callback function.
+ * @param {boolean} callOnce Whether the listener is a one-off
+ *     listener or otherwise.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @param {Object=} opt_handler Element in whose scope to call the listener.
+ * @return {goog.events.ListenableKey} Unique key for the listener.
+ * @template EVENTOBJ
+ * @private
+ */
+goog.events.listen_ = function(
+    src, type, listener, callOnce, opt_options, opt_handler) {
+  'use strict';
+  if (!type) {
+    throw new Error('Invalid event type');
+  }
+
+  var capture =
+      goog.isObject(opt_options) ? !!opt_options.capture : !!opt_options;
+
+  var listenerMap = goog.events.getListenerMap_(src);
+  if (!listenerMap) {
+    src[goog.events.LISTENER_MAP_PROP_] = listenerMap =
+        new goog.events.ListenerMap(src);
+  }
+
+  var listenerObj = /** @type {goog.events.Listener} */ (
+      listenerMap.add(type, listener, callOnce, capture, opt_handler));
+
+  // If the listenerObj already has a proxy, it has been set up
+  // previously. We simply return.
+  if (listenerObj.proxy) {
+    return listenerObj;
+  }
+
+  var proxy = goog.events.getProxy();
+  listenerObj.proxy = proxy;
+
+  proxy.src = src;
+  proxy.listener = listenerObj;
+
+  // Attach the proxy through the browser's API
+  if (src.addEventListener) {
+    // Don't pass an object as `capture` if the browser doesn't support that.
+    if (!goog.events.BrowserFeature.PASSIVE_EVENTS) {
+      opt_options = capture;
+    }
+    // Don't break tests that expect a boolean.
+    if (opt_options === undefined) opt_options = false;
+    src.addEventListener(type.toString(), proxy, opt_options);
+  } else if (src.attachEvent) {
+    // The else if above used to be an unconditional else. It would call
+    // attachEvent come gws or high water. This would sometimes throw an
+    // exception on IE11, spoiling the day of some callers. The previous
+    // incarnation of this code, from 2007, indicates that it replaced an
+    // earlier still version that caused excess allocations on IE6.
+    src.attachEvent(goog.events.getOnString_(type.toString()), proxy);
+  } else if (src.addListener && src.removeListener) {
+    // In IE, MediaQueryList uses addListener() insteadd of addEventListener. In
+    // Safari, there is no global for the MediaQueryList constructor, so we just
+    // check whether the object "looks like" MediaQueryList.
+    goog.asserts.assert(
+        type === 'change', 'MediaQueryList only has a change event');
+    src.addListener(proxy);
+  } else {
+    throw new Error('addEventListener and attachEvent are unavailable.');
+  }
+
+  goog.events.listenerCountEstimate_++;
+  return listenerObj;
+};
+
+
+/**
+ * Helper function for returning a proxy function.
+ * @return {!Function} A new or reused function object.
+ */
+goog.events.getProxy = function() {
+  'use strict';
+  const proxyCallbackFunction = goog.events.handleBrowserEvent_;
+  const f = function(eventObject) {
+    return proxyCallbackFunction.call(f.src, f.listener, eventObject);
+  };
+  return f;
+};
+
+
+/**
+ * Adds an event listener for a specific event on a native event
+ * target (such as a DOM element) or an object that has implemented
+ * {@link goog.events.Listenable}. After the event has fired the event
+ * listener is removed from the target.
+ *
+ * If an existing listener already exists, listenOnce will do
+ * nothing. In particular, if the listener was previously registered
+ * via listen(), listenOnce() will not turn the listener into a
+ * one-off listener. Similarly, if there is already an existing
+ * one-off listener, listenOnce does not modify the listeners (it is
+ * still a once listener).
+ *
+ * @param {EventTarget|goog.events.Listenable} src The node to listen
+ *     to events on.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type or array of event types.
+ * @param {function(this:T, EVENTOBJ):?|{handleEvent:function(?):?}|null}
+ *     listener Callback method.
+ * @param {(boolean|!AddEventListenerOptions)=} opt_options
+ * @param {T=} opt_handler Element in whose scope to call the listener.
+ * @return {goog.events.Key} Unique key for the listener.
+ * @template T,EVENTOBJ
+ */
+goog.events.listenOnce = function(
+    src, type, listener, opt_options, opt_handler) {
+  'use strict';
+  if (Array.isArray(type)) {
+    for (var i = 0; i < type.length; i++) {
+      goog.events.listenOnce(src, type[i], listener, opt_options, opt_handler);
+    }
+    return null;
+  }
+
+  listener = goog.events.wrapListener(listener);
+  if (goog.events.Listenable.isImplementedBy(src)) {
+    var capture =
+        goog.isObject(opt_options) ? !!opt_options.capture : !!opt_options;
+    return src.listenOnce(
+        /** @type {string|!goog.events.EventId} */ (type), listener, capture,
+        opt_handler);
+  } else {
+    return goog.events.listen_(
+        /** @type {!EventTarget} */ (src), type, listener,
+        /* callOnce */ true, opt_options, opt_handler);
+  }
+};
+
+
+/**
+ * Adds an event listener with a specific event wrapper on a DOM Node or an
+ * object that has implemented {@link goog.events.Listenable}. A listener can
+ * only be added once to an object.
+ *
+ * @param {EventTarget|goog.events.Listenable} src The target to
+ *     listen to events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(this:T, ?):?|{handleEvent:function(?):?}|null} listener
+ *     Callback method, or an object with a handleEvent function.
+ * @param {boolean=} opt_capt Whether to fire in capture phase (defaults to
+ *     false).
+ * @param {T=} opt_handler Element in whose scope to call the listener.
+ * @template T
+ */
+goog.events.listenWithWrapper = function(
+    src, wrapper, listener, opt_capt, opt_handler) {
+  'use strict';
+  wrapper.listen(src, listener, opt_capt, opt_handler);
+};
+
+
+/**
+ * Removes an event listener which was added with listen().
+ *
+ * @param {EventTarget|goog.events.Listenable} src The target to stop
+ *     listening to events on.
+ * @param {string|Array<string>|
+ *     !goog.events.EventId<EVENTOBJ>|!Array<!goog.events.EventId<EVENTOBJ>>}
+ *     type Event type or array of event types to unlisten to.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener The
+ *     listener function to remove.
+ * @param {(boolean|!EventListenerOptions)=} opt_options
+ *     whether the listener is fired during the capture or bubble phase of the
+ *     event.
+ * @param {Object=} opt_handler Element in whose scope to call the listener.
+ * @return {?boolean} indicating whether the listener was there to remove.
+ * @template EVENTOBJ
+ */
+goog.events.unlisten = function(src, type, listener, opt_options, opt_handler) {
+  'use strict';
+  if (Array.isArray(type)) {
+    for (var i = 0; i < type.length; i++) {
+      goog.events.unlisten(src, type[i], listener, opt_options, opt_handler);
+    }
+    return null;
+  }
+  var capture =
+      goog.isObject(opt_options) ? !!opt_options.capture : !!opt_options;
+
+  listener = goog.events.wrapListener(listener);
+  if (goog.events.Listenable.isImplementedBy(src)) {
+    return src.unlisten(
+        /** @type {string|!goog.events.EventId} */ (type), listener, capture,
+        opt_handler);
+  }
+
+  if (!src) {
+    // TODO(chrishenry): We should tighten the API to only accept
+    // non-null objects, or add an assertion here.
+    return false;
+  }
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {!EventTarget} */ (src));
+  if (listenerMap) {
+    var listenerObj = listenerMap.getListener(
+        /** @type {string|!goog.events.EventId} */ (type), listener, capture,
+        opt_handler);
+    if (listenerObj) {
+      return goog.events.unlistenByKey(listenerObj);
+    }
+  }
+
+  return false;
+};
+
+
+/**
+ * Removes an event listener which was added with listen() by the key
+ * returned by listen().
+ *
+ * @param {goog.events.Key} key The key returned by listen() for this
+ *     event listener.
+ * @return {boolean} indicating whether the listener was there to remove.
+ */
+goog.events.unlistenByKey = function(key) {
+  'use strict';
+  // TODO(chrishenry): Remove this check when tests that rely on this
+  // are fixed.
+  if (typeof key === 'number') {
+    return false;
+  }
+
+  var listener = key;
+  if (!listener || listener.removed) {
+    return false;
+  }
+
+  var src = listener.src;
+  if (goog.events.Listenable.isImplementedBy(src)) {
+    return /** @type {!goog.events.Listenable} */ (src).unlistenByKey(listener);
+  }
+
+  var type = listener.type;
+  var proxy = listener.proxy;
+  if (src.removeEventListener) {
+    src.removeEventListener(type, proxy, listener.capture);
+  } else if (src.detachEvent) {
+    src.detachEvent(goog.events.getOnString_(type), proxy);
+  } else if (src.addListener && src.removeListener) {
+    src.removeListener(proxy);
+  }
+  goog.events.listenerCountEstimate_--;
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {!EventTarget} */ (src));
+  // TODO(chrishenry): Try to remove this conditional and execute the
+  // first branch always. This should be safe.
+  if (listenerMap) {
+    listenerMap.removeByKey(listener);
+    if (listenerMap.getTypeCount() == 0) {
+      // Null the src, just because this is simple to do (and useful
+      // for IE <= 7).
+      listenerMap.src = null;
+      // We don't use delete here because IE does not allow delete
+      // on a window object.
+      src[goog.events.LISTENER_MAP_PROP_] = null;
+    }
+  } else {
+    /** @type {!goog.events.Listener} */ (listener).markAsRemoved();
+  }
+
+  return true;
+};
+
+
+/**
+ * Removes an event listener which was added with listenWithWrapper().
+ *
+ * @param {EventTarget|goog.events.Listenable} src The target to stop
+ *     listening to events on.
+ * @param {goog.events.EventWrapper} wrapper Event wrapper to use.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener The
+ *     listener function to remove.
+ * @param {boolean=} opt_capt In DOM-compliant browsers, this determines
+ *     whether the listener is fired during the capture or bubble phase of the
+ *     event.
+ * @param {Object=} opt_handler Element in whose scope to call the listener.
+ */
+goog.events.unlistenWithWrapper = function(
+    src, wrapper, listener, opt_capt, opt_handler) {
+  'use strict';
+  wrapper.unlisten(src, listener, opt_capt, opt_handler);
+};
+
+
+/**
+ * Removes all listeners from an object. You can also optionally
+ * remove listeners of a particular type.
+ *
+ * @param {Object|undefined} obj Object to remove listeners from. Must be an
+ *     EventTarget or a goog.events.Listenable.
+ * @param {string|!goog.events.EventId=} opt_type Type of event to remove.
+ *     Default is all types.
+ * @return {number} Number of listeners removed.
+ */
+goog.events.removeAll = function(obj, opt_type) {
+  'use strict';
+  // TODO(chrishenry): Change the type of obj to
+  // (!EventTarget|!goog.events.Listenable).
+
+  if (!obj) {
+    return 0;
+  }
+
+  if (goog.events.Listenable.isImplementedBy(obj)) {
+    return /** @type {?} */ (obj).removeAllListeners(opt_type);
+  }
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {!EventTarget} */ (obj));
+  if (!listenerMap) {
+    return 0;
+  }
+
+  var count = 0;
+  var typeStr = opt_type && opt_type.toString();
+  for (var type in listenerMap.listeners) {
+    if (!typeStr || type == typeStr) {
+      // Clone so that we don't need to worry about unlistenByKey
+      // changing the content of the ListenerMap.
+      var listeners = listenerMap.listeners[type].concat();
+      for (var i = 0; i < listeners.length; ++i) {
+        if (goog.events.unlistenByKey(listeners[i])) {
+          ++count;
+        }
+      }
+    }
+  }
+  return count;
+};
+
+
+/**
+ * Gets the listeners for a given object, type and capture phase.
+ *
+ * @param {Object} obj Object to get listeners for.
+ * @param {string|!goog.events.EventId} type Event type.
+ * @param {boolean} capture Capture phase?.
+ * @return {!Array<!goog.events.Listener>} Array of listener objects.
+ */
+goog.events.getListeners = function(obj, type, capture) {
+  'use strict';
+  if (goog.events.Listenable.isImplementedBy(obj)) {
+    return /** @type {!goog.events.Listenable} */ (obj).getListeners(
+        type, capture);
+  } else {
+    if (!obj) {
+      // TODO(chrishenry): We should tighten the API to accept
+      // !EventTarget|goog.events.Listenable, and add an assertion here.
+      return [];
+    }
+
+    var listenerMap = goog.events.getListenerMap_(
+        /** @type {!EventTarget} */ (obj));
+    return listenerMap ? listenerMap.getListeners(type, capture) : [];
+  }
+};
+
+
+/**
+ * Gets the goog.events.Listener for the event or null if no such listener is
+ * in use.
+ *
+ * @param {EventTarget|goog.events.Listenable} src The target from
+ *     which to get listeners.
+ * @param {?string|!goog.events.EventId<EVENTOBJ>} type The type of the event.
+ * @param {function(EVENTOBJ):?|{handleEvent:function(?):?}|null} listener The
+ *     listener function to get.
+ * @param {boolean=} opt_capt In DOM-compliant browsers, this determines
+ *                            whether the listener is fired during the
+ *                            capture or bubble phase of the event.
+ * @param {Object=} opt_handler Element in whose scope to call the listener.
+ * @return {goog.events.ListenableKey} the found listener or null if not found.
+ * @template EVENTOBJ
+ */
+goog.events.getListener = function(src, type, listener, opt_capt, opt_handler) {
+  'use strict';
+  // TODO(chrishenry): Change type from ?string to string, or add assertion.
+  type = /** @type {string} */ (type);
+  listener = goog.events.wrapListener(listener);
+  var capture = !!opt_capt;
+  if (goog.events.Listenable.isImplementedBy(src)) {
+    return src.getListener(type, listener, capture, opt_handler);
+  }
+
+  if (!src) {
+    // TODO(chrishenry): We should tighten the API to only accept
+    // non-null objects, or add an assertion here.
+    return null;
+  }
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {!EventTarget} */ (src));
+  if (listenerMap) {
+    return listenerMap.getListener(type, listener, capture, opt_handler);
+  }
+  return null;
+};
+
+
+/**
+ * Returns whether an event target has any active listeners matching the
+ * specified signature. If either the type or capture parameters are
+ * unspecified, the function will match on the remaining criteria.
+ *
+ * @param {EventTarget|goog.events.Listenable} obj Target to get
+ *     listeners for.
+ * @param {string|!goog.events.EventId=} opt_type Event type.
+ * @param {boolean=} opt_capture Whether to check for capture or bubble-phase
+ *     listeners.
+ * @return {boolean} Whether an event target has one or more listeners matching
+ *     the requested type and/or capture phase.
+ */
+goog.events.hasListener = function(obj, opt_type, opt_capture) {
+  'use strict';
+  if (goog.events.Listenable.isImplementedBy(obj)) {
+    return obj.hasListener(opt_type, opt_capture);
+  }
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {!EventTarget} */ (obj));
+  return !!listenerMap && listenerMap.hasListener(opt_type, opt_capture);
+};
+
+
+/**
+ * Provides a nice string showing the normalized event objects public members
+ * @param {Object} e Event Object.
+ * @return {string} String of the public members of the normalized event object.
+ */
+goog.events.expose = function(e) {
+  'use strict';
+  var str = [];
+  for (var key in e) {
+    if (e[key] && e[key].id) {
+      str.push(key + ' = ' + e[key] + ' (' + e[key].id + ')');
+    } else {
+      str.push(key + ' = ' + e[key]);
+    }
+  }
+  return str.join('\n');
+};
+
+
+/**
+ * Returns a string with on prepended to the specified type. This is used for IE
+ * which expects "on" to be prepended. This function caches the string in order
+ * to avoid extra allocations in steady state.
+ * @param {string} type Event type.
+ * @return {string} The type string with 'on' prepended.
+ * @private
+ */
+goog.events.getOnString_ = function(type) {
+  'use strict';
+  if (type in goog.events.onStringMap_) {
+    return goog.events.onStringMap_[type];
+  }
+  return goog.events.onStringMap_[type] = goog.events.onString_ + type;
+};
+
+
+/**
+ * Fires an object's listeners of a particular type and phase
+ *
+ * @param {Object} obj Object whose listeners to call.
+ * @param {string|!goog.events.EventId} type Event type.
+ * @param {boolean} capture Which event phase.
+ * @param {Object} eventObject Event object to be passed to listener.
+ * @return {boolean} True if all listeners returned true else false.
+ */
+goog.events.fireListeners = function(obj, type, capture, eventObject) {
+  'use strict';
+  if (goog.events.Listenable.isImplementedBy(obj)) {
+    return /** @type {!goog.events.Listenable} */ (obj).fireListeners(
+        type, capture, eventObject);
+  }
+
+  return goog.events.fireListeners_(obj, type, capture, eventObject);
+};
+
+
+/**
+ * Fires an object's listeners of a particular type and phase.
+ * @param {Object} obj Object whose listeners to call.
+ * @param {string|!goog.events.EventId} type Event type.
+ * @param {boolean} capture Which event phase.
+ * @param {Object} eventObject Event object to be passed to listener.
+ * @return {boolean} True if all listeners returned true else false.
+ * @private
+ */
+goog.events.fireListeners_ = function(obj, type, capture, eventObject) {
+  'use strict';
+  /** @type {boolean} */
+  var retval = true;
+
+  var listenerMap = goog.events.getListenerMap_(
+      /** @type {EventTarget} */ (obj));
+  if (listenerMap) {
+    // TODO(chrishenry): Original code avoids array creation when there
+    // is no listener, so we do the same. If this optimization turns
+    // out to be not required, we can replace this with
+    // listenerMap.getListeners(type, capture) instead, which is simpler.
+    var listenerArray = listenerMap.listeners[type.toString()];
+    if (listenerArray) {
+      listenerArray = listenerArray.concat();
+      for (var i = 0; i < listenerArray.length; i++) {
+        var listener = listenerArray[i];
+        // We might not have a listener if the listener was removed.
+        if (listener && listener.capture == capture && !listener.removed) {
+          var result = goog.events.fireListener(listener, eventObject);
+          retval = retval && (result !== false);
+        }
+      }
+    }
+  }
+  return retval;
+};
+
+
+/**
+ * Fires a listener with a set of arguments
+ *
+ * @param {goog.events.Listener} listener The listener object to call.
+ * @param {Object} eventObject The event object to pass to the listener.
+ * @return {*} Result of listener.
+ */
+goog.events.fireListener = function(listener, eventObject) {
+  'use strict';
+  var listenerFn = listener.listener;
+  var listenerHandler = listener.handler || listener.src;
+
+  if (listener.callOnce) {
+    goog.events.unlistenByKey(listener);
+  }
+  return listenerFn.call(listenerHandler, eventObject);
+};
+
+
+/**
+ * Gets the total number of listeners currently in the system.
+ * @return {number} Number of listeners.
+ * @deprecated This returns estimated count, now that Closure no longer
+ * stores a central listener registry. We still return an estimation
+ * to keep existing listener-related tests passing. In the near future,
+ * this function will be removed.
+ */
+goog.events.getTotalListenerCount = function() {
+  'use strict';
+  return goog.events.listenerCountEstimate_;
+};
+
+
+/**
+ * Dispatches an event (or event like object) and calls all listeners
+ * listening for events of this type. The type of the event is decided by the
+ * type property on the event object.
+ *
+ * If any of the listeners returns false OR calls preventDefault then this
+ * function will return false.  If one of the capture listeners calls
+ * stopPropagation, then the bubble listeners won't fire.
+ *
+ * @param {goog.events.Listenable} src The event target.
+ * @param {goog.events.EventLike} e Event object.
+ * @return {boolean} If anyone called preventDefault on the event object (or
+ *     if any of the handlers returns false) this will also return false.
+ *     If there are no handlers, or if all handlers return true, this returns
+ *     true.
+ */
+goog.events.dispatchEvent = function(src, e) {
+  'use strict';
+  goog.asserts.assert(
+      goog.events.Listenable.isImplementedBy(src),
+      'Can not use goog.events.dispatchEvent with ' +
+          'non-goog.events.Listenable instance.');
+  return src.dispatchEvent(e);
+};
+
+
+/**
+ * Installs exception protection for the browser event entry point using the
+ * given error handler.
+ *
+ * @param {goog.debug.ErrorHandler} errorHandler Error handler with which to
+ *     protect the entry point.
+ */
+goog.events.protectBrowserEventEntryPoint = function(errorHandler) {
+  'use strict';
+  goog.events.handleBrowserEvent_ =
+      errorHandler.protectEntryPoint(goog.events.handleBrowserEvent_);
+};
+
+
+/**
+ * Handles an event and dispatches it to the correct listeners. This
+ * function is a proxy for the real listener the user specified.
+ *
+ * @param {goog.events.Listener} listener The listener object.
+ * @param {Event=} opt_evt Optional event object that gets passed in via the
+ *     native event handlers.
+ * @return {*} Result of the event handler.
+ * @this {EventTarget} The object or Element that fired the event.
+ * @private
+ */
+goog.events.handleBrowserEvent_ = function(listener, opt_evt) {
+  'use strict';
+  if (listener.removed) {
+    return true;
+  }
+
+  // Otherwise, simply fire the listener.
+  return goog.events.fireListener(
+      listener, new goog.events.BrowserEvent(opt_evt, this));
+};
+
+
+/**
+ * This is used to mark the IE event object so we do not do the Closure pass
+ * twice for a bubbling event.
+ * @param {Event} e The IE browser event.
+ * @private
+ */
+goog.events.markIeEvent_ = function(e) {
+  'use strict';
+  // Only the keyCode and the returnValue can be changed. We use keyCode for
+  // non keyboard events.
+  // event.returnValue is a bit more tricky. It is undefined by default. A
+  // boolean false prevents the default action. In a window.onbeforeunload and
+  // the returnValue is non undefined it will be alerted. However, we will only
+  // modify the returnValue for keyboard events. We can get a problem if non
+  // closure events sets the keyCode or the returnValue
+
+  var useReturnValue = false;
+
+  if (e.keyCode == 0) {
+    // We cannot change the keyCode in case that srcElement is input[type=file].
+    // We could test that that is the case but that would allocate 3 objects.
+    // If we use try/catch we will only allocate extra objects in the case of a
+    // failure.
+
+    try {
+      e.keyCode = -1;
+      return;
+    } catch (ex) {
+      useReturnValue = true;
+    }
+  }
+
+  if (useReturnValue ||
+      /** @type {boolean|undefined} */ (e.returnValue) == undefined) {
+    e.returnValue = true;
+  }
+};
+
+
+/**
+ * This is used to check if an IE event has already been handled by the Closure
+ * system so we do not do the Closure pass twice for a bubbling event.
+ * @param {Event} e  The IE browser event.
+ * @return {boolean} True if the event object has been marked.
+ * @private
+ */
+goog.events.isMarkedIeEvent_ = function(e) {
+  'use strict';
+  return e.keyCode < 0 || e.returnValue != undefined;
+};
+
+
+/**
+ * Counter to create unique event ids.
+ * @private {number}
+ */
+goog.events.uniqueIdCounter_ = 0;
+
+
+/**
+ * Creates a unique event id.
+ *
+ * @param {string} identifier The identifier.
+ * @return {string} A unique identifier.
+ * @idGenerator {unique}
+ */
+goog.events.getUniqueId = function(identifier) {
+  'use strict';
+  return identifier + '_' + goog.events.uniqueIdCounter_++;
+};
+
+
+/**
+ * @param {EventTarget} src The source object.
+ * @return {goog.events.ListenerMap} A listener map for the given
+ *     source object, or null if none exists.
+ * @private
+ */
+goog.events.getListenerMap_ = function(src) {
+  'use strict';
+  var listenerMap = src[goog.events.LISTENER_MAP_PROP_];
+  // IE serializes the property as well (e.g. when serializing outer
+  // HTML). So we must check that the value is of the correct type.
+  return listenerMap instanceof goog.events.ListenerMap ? listenerMap : null;
+};
+
+
+/**
+ * Expando property for listener function wrapper for Object with
+ * handleEvent.
+ * @private @const {string}
+ */
+goog.events.LISTENER_WRAPPER_PROP_ =
+    '__closure_events_fn_' + ((Math.random() * 1e9) >>> 0);
+
+
+/**
+ * @param {Object|Function} listener The listener function or an
+ *     object that contains handleEvent method.
+ * @return {!Function} Either the original function or a function that
+ *     calls obj.handleEvent. If the same listener is passed to this
+ *     function more than once, the same function is guaranteed to be
+ *     returned.
+ */
+goog.events.wrapListener = function(listener) {
+  'use strict';
+  goog.asserts.assert(listener, 'Listener can not be null.');
+
+  if (typeof listener === 'function') {
+    return listener;
+  }
+
+  goog.asserts.assert(
+      listener.handleEvent, 'An object listener must have handleEvent method.');
+  if (!listener[goog.events.LISTENER_WRAPPER_PROP_]) {
+    listener[goog.events.LISTENER_WRAPPER_PROP_] = function(e) {
+      'use strict';
+      return /** @type {?} */ (listener).handleEvent(e);
+    };
+  }
+  return listener[goog.events.LISTENER_WRAPPER_PROP_];
+};
+
+
+// Register the browser event handler as an entry point, so that
+// it can be monitored for exception handling, etc.
+goog.debug.entryPointRegistry.register(
+    /**
+     * @param {function(!Function): !Function} transformer The transforming
+     *     function.
+     */
+    function(transformer) {
+      'use strict';
+      goog.events.handleBrowserEvent_ =
+          transformer(goog.events.handleBrowserEvent_);
+    });

js/goog/events/eventtarget.js

@@ -0,0 +1,495 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A disposable implementation of a custom
+ * listenable/event target. See also: documentation for
+ * `goog.events.Listenable`.
+ *
+ * @see ../demos/eventtarget.html
+ * @see goog.events.Listenable
+ */
+
+goog.provide('goog.events.EventTarget');
+
+goog.require('goog.Disposable');
+goog.require('goog.asserts');
+goog.require('goog.events');
+goog.require('goog.events.Event');
+goog.require('goog.events.Listenable');
+goog.require('goog.events.ListenerMap');
+goog.require('goog.object');
+goog.requireType('goog.events.EventId');
+goog.requireType('goog.events.EventLike');
+goog.requireType('goog.events.ListenableKey');
+
+
+
+/**
+ * An implementation of `goog.events.Listenable` with full W3C
+ * EventTarget-like support (capture/bubble mechanism, stopping event
+ * propagation, preventing default actions).
+ *
+ * You may subclass this class to turn your class into a Listenable.
+ *
+ * Unless propagation is stopped, an event dispatched by an
+ * EventTarget will bubble to the parent returned by
+ * `getParentEventTarget`. To set the parent, call
+ * `setParentEventTarget`. Subclasses that don't support
+ * changing the parent can override the setter to throw an error.
+ *
+ * Example usage:
+ * <pre>
+ *   var source = new goog.events.EventTarget();
+ *   function handleEvent(e) {
+ *     alert('Type: ' + e.type + '; Target: ' + e.target);
+ *   }
+ *   source.listen('foo', handleEvent);
+ *   // Or: goog.events.listen(source, 'foo', handleEvent);
+ *   ...
+ *   source.dispatchEvent('foo');  // will call handleEvent
+ *   ...
+ *   source.unlisten('foo', handleEvent);
+ *   // Or: goog.events.unlisten(source, 'foo', handleEvent);
+ * </pre>
+ *
+ * @constructor
+ * @extends {goog.Disposable}
+ * @implements {goog.events.Listenable}
+ */
+goog.events.EventTarget = function() {
+  'use strict';
+  goog.Disposable.call(this);
+
+  /**
+   * Maps of event type to an array of listeners.
+   * @private {!goog.events.ListenerMap}
+   */
+  this.eventTargetListeners_ = new goog.events.ListenerMap(this);
+
+  /**
+   * The object to use for event.target. Useful when mixing in an
+   * EventTarget to another object.
+   * @private {!Object}
+   */
+  this.actualEventTarget_ = this;
+
+  /**
+   * Parent event target, used during event bubbling.
+   *
+   * TODO(chrishenry): Change this to goog.events.Listenable. This
+   * currently breaks people who expect getParentEventTarget to return
+   * goog.events.EventTarget.
+   *
+   * @private {?goog.events.EventTarget}
+   */
+  this.parentEventTarget_ = null;
+};
+goog.inherits(goog.events.EventTarget, goog.Disposable);
+goog.events.Listenable.addImplementation(goog.events.EventTarget);
+
+
+/**
+ * An artificial cap on the number of ancestors you can have. This is mainly
+ * for loop detection.
+ * @const {number}
+ * @private
+ */
+goog.events.EventTarget.MAX_ANCESTORS_ = 1000;
+
+
+/**
+ * Returns the parent of this event target to use for bubbling.
+ *
+ * @return {goog.events.EventTarget} The parent EventTarget or null if
+ *     there is no parent.
+ * @override
+ */
+goog.events.EventTarget.prototype.getParentEventTarget = function() {
+  'use strict';
+  return this.parentEventTarget_;
+};
+
+
+/**
+ * Sets the parent of this event target to use for capture/bubble
+ * mechanism.
+ * @param {goog.events.EventTarget} parent Parent listenable (null if none).
+ */
+goog.events.EventTarget.prototype.setParentEventTarget = function(parent) {
+  'use strict';
+  this.parentEventTarget_ = parent;
+};
+
+
+/**
+ * Adds an event listener to the event target. The same handler can only be
+ * added once per the type. Even if you add the same handler multiple times
+ * using the same type then it will only be called once when the event is
+ * dispatched.
+ *
+ * @param {string|!goog.events.EventId} type The type of the event to listen for
+ * @param {function(?):?|{handleEvent:function(?):?}|null} handler The function
+ *     to handle the event. The handler can also be an object that implements
+ *     the handleEvent method which takes the event object as argument.
+ * @param {boolean=} opt_capture In DOM-compliant browsers, this determines
+ *     whether the listener is fired during the capture or bubble phase
+ *     of the event.
+ * @param {Object=} opt_handlerScope Object in whose scope to call
+ *     the listener.
+ * @deprecated Use `#listen` instead, when possible. Otherwise, use
+ *     `goog.events.listen` if you are passing Object
+ *     (instead of Function) as handler.
+ */
+goog.events.EventTarget.prototype.addEventListener = function(
+    type, handler, opt_capture, opt_handlerScope) {
+  'use strict';
+  goog.events.listen(this, type, handler, opt_capture, opt_handlerScope);
+};
+
+
+/**
+ * Removes an event listener from the event target. The handler must be the
+ * same object as the one added. If the handler has not been added then
+ * nothing is done.
+ *
+ * @param {string|!goog.events.EventId} type The type of the event to listen for
+ * @param {function(?):?|{handleEvent:function(?):?}|null} handler The function
+ *     to handle the event. The handler can also be an object that implements
+ *     the handleEvent method which takes the event object as argument.
+ * @param {boolean=} opt_capture In DOM-compliant browsers, this determines
+ *     whether the listener is fired during the capture or bubble phase
+ *     of the event.
+ * @param {Object=} opt_handlerScope Object in whose scope to call
+ *     the listener.
+ * @deprecated Use `#unlisten` instead, when possible. Otherwise, use
+ *     `goog.events.unlisten` if you are passing Object
+ *     (instead of Function) as handler.
+ */
+goog.events.EventTarget.prototype.removeEventListener = function(
+    type, handler, opt_capture, opt_handlerScope) {
+  'use strict';
+  goog.events.unlisten(this, type, handler, opt_capture, opt_handlerScope);
+};
+
+
+/**
+ * @param {?goog.events.EventLike} e Event object.
+ * @return {boolean} If anyone called preventDefault on the event object (or
+ *     if any of the listeners returns false) this will also return false.
+ * @override
+ */
+goog.events.EventTarget.prototype.dispatchEvent = function(e) {
+  'use strict';
+  this.assertInitialized_();
+
+  var ancestorsTree, ancestor = this.getParentEventTarget();
+  if (ancestor) {
+    ancestorsTree = [];
+    var ancestorCount = 1;
+    for (; ancestor; ancestor = ancestor.getParentEventTarget()) {
+      ancestorsTree.push(ancestor);
+      goog.asserts.assert(
+          (++ancestorCount < goog.events.EventTarget.MAX_ANCESTORS_),
+          'infinite loop');
+    }
+  }
+
+  return goog.events.EventTarget.dispatchEventInternal_(
+      this.actualEventTarget_, e, ancestorsTree);
+};
+
+
+/**
+ * Removes listeners from this object.  Classes that extend EventTarget may
+ * need to override this method in order to remove references to DOM Elements
+ * and additional listeners.
+ * @override
+ * @protected
+ */
+goog.events.EventTarget.prototype.disposeInternal = function() {
+  'use strict';
+  goog.events.EventTarget.superClass_.disposeInternal.call(this);
+
+  this.removeAllListeners();
+  this.parentEventTarget_ = null;
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {!goog.events.ListenableKey} Unique key for the listener.
+ * @template SCOPE,EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.listen = function(
+    type, listener, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  this.assertInitialized_();
+  return this.eventTargetListeners_.add(
+      String(type), listener, false /* callOnce */, opt_useCapture,
+      opt_listenerScope);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {!goog.events.ListenableKey} Unique key for the listener.
+ * @template SCOPE,EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.listenOnce = function(
+    type, listener, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  return this.eventTargetListeners_.add(
+      String(type), listener, true /* callOnce */, opt_useCapture,
+      opt_listenerScope);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call
+ *     the listener.
+ * @return {boolean} Whether any listener was removed.
+ * @template SCOPE,EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.unlisten = function(
+    type, listener, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  return this.eventTargetListeners_.remove(
+      String(type), listener, opt_useCapture, opt_listenerScope);
+};
+
+
+/**
+ * @param {!goog.events.ListenableKey} key The key returned by
+ *     listen() or listenOnce().
+ * @return {boolean} Whether any listener was removed.
+ * @override
+ */
+goog.events.EventTarget.prototype.unlistenByKey = function(key) {
+  'use strict';
+  return this.eventTargetListeners_.removeByKey(key);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId=} opt_type Type of event to remove,
+ *     default is to remove all types.
+ * @return {number} Number of listeners removed.
+ * @override
+ */
+goog.events.EventTarget.prototype.removeAllListeners = function(opt_type) {
+  'use strict';
+  // TODO(chrishenry): Previously, removeAllListeners can be called on
+  // uninitialized EventTarget, so we preserve that behavior. We
+  // should remove this when usages that rely on that fact are purged.
+  if (!this.eventTargetListeners_) {
+    return 0;
+  }
+  return this.eventTargetListeners_.removeAll(opt_type);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The type of the
+ *     listeners to fire.
+ * @param {boolean} capture The capture mode of the listeners to fire.
+ * @param {EVENTOBJ} eventObject The event object to fire.
+ * @return {boolean} Whether all listeners succeeded without
+ *     attempting to prevent default behavior. If any listener returns
+ *     false or called goog.events.Event#preventDefault, this returns
+ *     false.
+ * @template EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.fireListeners = function(
+    type, capture, eventObject) {
+  'use strict';
+  // TODO(chrishenry): Original code avoids array creation when there
+  // is no listener, so we do the same. If this optimization turns
+  // out to be not required, we can replace this with
+  // getListeners(type, capture) instead, which is simpler.
+  var listenerArray = this.eventTargetListeners_.listeners[String(type)];
+  if (!listenerArray) {
+    return true;
+  }
+  listenerArray = listenerArray.concat();
+
+  var rv = true;
+  for (var i = 0; i < listenerArray.length; ++i) {
+    var listener = listenerArray[i];
+    // We might not have a listener if the listener was removed.
+    if (listener && !listener.removed && listener.capture == capture) {
+      var listenerFn = listener.listener;
+      var listenerHandler = listener.handler || listener.src;
+
+      if (listener.callOnce) {
+        this.unlistenByKey(listener);
+      }
+      rv = listenerFn.call(listenerHandler, eventObject) !== false && rv;
+    }
+  }
+
+  return rv && !eventObject.defaultPrevented;
+};
+
+
+/**
+ * @param {string|!goog.events.EventId} type The type of the listeners to fire.
+ * @param {boolean} capture The capture mode of the listeners to fire.
+ * @return {!Array<!goog.events.ListenableKey>} An array of registered
+ *     listeners.
+ * @template EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.getListeners = function(type, capture) {
+  'use strict';
+  return this.eventTargetListeners_.getListeners(String(type), capture);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The name of the event
+ *     without the 'on' prefix.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener The
+ *     listener function to get.
+ * @param {boolean} capture Whether the listener is a capturing listener.
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {?goog.events.ListenableKey} the found listener or null if not found.
+ * @template SCOPE,EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.getListener = function(
+    type, listener, capture, opt_listenerScope) {
+  'use strict';
+  return this.eventTargetListeners_.getListener(
+      String(type), listener, capture, opt_listenerScope);
+};
+
+
+/**
+ * @param {string|!goog.events.EventId<EVENTOBJ>=} opt_type Event type.
+ * @param {boolean=} opt_capture Whether to check for capture or bubble
+ *     listeners.
+ * @return {boolean} Whether there is any active listeners matching
+ *     the requested type and/or capture phase.
+ * @template EVENTOBJ
+ * @override
+ */
+goog.events.EventTarget.prototype.hasListener = function(
+    opt_type, opt_capture) {
+  'use strict';
+  var id = (opt_type !== undefined) ? String(opt_type) : undefined;
+  return this.eventTargetListeners_.hasListener(id, opt_capture);
+};
+
+
+/**
+ * Sets the target to be used for `event.target` when firing
+ * event. Mainly used for testing. For example, see
+ * `goog.testing.events.mixinListenable`.
+ * @param {!Object} target The target.
+ */
+goog.events.EventTarget.prototype.setTargetForTesting = function(target) {
+  'use strict';
+  this.actualEventTarget_ = target;
+};
+
+
+/**
+ * Asserts that the event target instance is initialized properly.
+ * @private
+ */
+goog.events.EventTarget.prototype.assertInitialized_ = function() {
+  'use strict';
+  goog.asserts.assert(
+      this.eventTargetListeners_,
+      'Event target is not initialized. Did you call the superclass ' +
+          '(goog.events.EventTarget) constructor?');
+};
+
+
+/**
+ * Dispatches the given event on the ancestorsTree.
+ *
+ * @param {!Object} target The target to dispatch on.
+ * @param {goog.events.Event|Object|string} e The event object.
+ * @param {Array<goog.events.Listenable>=} opt_ancestorsTree The ancestors
+ *     tree of the target, in reverse order from the closest ancestor
+ *     to the root event target. May be null if the target has no ancestor.
+ * @return {boolean} If anyone called preventDefault on the event object (or
+ *     if any of the listeners returns false) this will also return false.
+ * @private
+ */
+goog.events.EventTarget.dispatchEventInternal_ = function(
+    target, e, opt_ancestorsTree) {
+  'use strict';
+  /** @suppress {missingProperties} */
+  var type = e.type || /** @type {string} */ (e);
+
+  // If accepting a string or object, create a custom event object so that
+  // preventDefault and stopPropagation work with the event.
+  if (typeof e === 'string') {
+    e = new goog.events.Event(e, target);
+  } else if (!(e instanceof goog.events.Event)) {
+    var oldEvent = e;
+    e = new goog.events.Event(type, target);
+    goog.object.extend(e, oldEvent);
+  } else {
+    e.target = e.target || target;
+  }
+
+  var rv = true, currentTarget;
+
+  // Executes all capture listeners on the ancestors, if any.
+  if (opt_ancestorsTree) {
+    for (var i = opt_ancestorsTree.length - 1;
+         !e.hasPropagationStopped() && i >= 0; i--) {
+      currentTarget = e.currentTarget = opt_ancestorsTree[i];
+      rv = currentTarget.fireListeners(type, true, e) && rv;
+    }
+  }
+
+  // Executes capture and bubble listeners on the target.
+  if (!e.hasPropagationStopped()) {
+    currentTarget = /** @type {?} */ (e.currentTarget = target);
+    rv = currentTarget.fireListeners(type, true, e) && rv;
+    if (!e.hasPropagationStopped()) {
+      rv = currentTarget.fireListeners(type, false, e) && rv;
+    }
+  }
+
+  // Executes all bubble listeners on the ancestors, if any.
+  if (opt_ancestorsTree) {
+    for (i = 0; !e.hasPropagationStopped() && i < opt_ancestorsTree.length;
+         i++) {
+      currentTarget = e.currentTarget = opt_ancestorsTree[i];
+      rv = currentTarget.fireListeners(type, false, e) && rv;
+    }
+  }
+
+  return rv;
+};

js/goog/events/eventtype.js

@@ -0,0 +1,437 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Event Types.
+ */
+
+
+goog.provide('goog.events.EventType');
+goog.provide('goog.events.MouseAsMouseEventType');
+goog.provide('goog.events.MouseEvents');
+goog.provide('goog.events.PointerAsMouseEventType');
+goog.provide('goog.events.PointerAsTouchEventType');
+goog.provide('goog.events.PointerFallbackEventType');
+goog.provide('goog.events.PointerTouchFallbackEventType');
+
+goog.require('goog.events.BrowserFeature');
+goog.require('goog.userAgent');
+
+
+/**
+ * Returns a prefixed event name for the current browser.
+ * @param {string} eventName The name of the event.
+ * @return {string} The prefixed event name.
+ * @private
+ */
+goog.events.getVendorPrefixedName_ = function(eventName) {
+  'use strict';
+  return goog.userAgent.WEBKIT ? 'webkit' + eventName : eventName.toLowerCase();
+};
+
+
+/**
+ * Constants for event names.
+ * @enum {string}
+ */
+goog.events.EventType = {
+  // Mouse events
+  CLICK: 'click',
+  RIGHTCLICK: 'rightclick',
+  DBLCLICK: 'dblclick',
+  AUXCLICK: 'auxclick',
+  MOUSEDOWN: 'mousedown',
+  MOUSEUP: 'mouseup',
+  MOUSEOVER: 'mouseover',
+  MOUSEOUT: 'mouseout',
+  MOUSEMOVE: 'mousemove',
+  MOUSEENTER: 'mouseenter',
+  MOUSELEAVE: 'mouseleave',
+
+  // Non-existent event; will never fire. This exists as a mouse counterpart to
+  // POINTERCANCEL.
+  MOUSECANCEL: 'mousecancel',
+
+  // Selection events.
+  // https://www.w3.org/TR/selection-api/
+  SELECTIONCHANGE: 'selectionchange',
+  SELECTSTART: 'selectstart',  // IE, Safari, Chrome
+
+  // Wheel events
+  // http://www.w3.org/TR/DOM-Level-3-Events/#events-wheelevents
+  WHEEL: 'wheel',
+
+  // Key events
+  KEYPRESS: 'keypress',
+  KEYDOWN: 'keydown',
+  KEYUP: 'keyup',
+
+  // Focus
+  BLUR: 'blur',
+  FOCUS: 'focus',
+  DEACTIVATE: 'deactivate',  // IE only
+  FOCUSIN: 'focusin',
+  FOCUSOUT: 'focusout',
+
+  // Forms
+  CHANGE: 'change',
+  RESET: 'reset',
+  SELECT: 'select',
+  SUBMIT: 'submit',
+  INPUT: 'input',
+  PROPERTYCHANGE: 'propertychange',  // IE only
+
+  // Drag and drop
+  DRAGSTART: 'dragstart',
+  DRAG: 'drag',
+  DRAGENTER: 'dragenter',
+  DRAGOVER: 'dragover',
+  DRAGLEAVE: 'dragleave',
+  DROP: 'drop',
+  DRAGEND: 'dragend',
+
+  // Touch events
+  // Note that other touch events exist, but we should follow the W3C list here.
+  // http://www.w3.org/TR/touch-events/#list-of-touchevent-types
+  TOUCHSTART: 'touchstart',
+  TOUCHMOVE: 'touchmove',
+  TOUCHEND: 'touchend',
+  TOUCHCANCEL: 'touchcancel',
+
+  // Misc
+  BEFOREUNLOAD: 'beforeunload',
+  CONSOLEMESSAGE: 'consolemessage',
+  CONTEXTMENU: 'contextmenu',
+  DEVICECHANGE: 'devicechange',
+  DEVICEMOTION: 'devicemotion',
+  DEVICEORIENTATION: 'deviceorientation',
+  DOMCONTENTLOADED: 'DOMContentLoaded',
+  ERROR: 'error',
+  HELP: 'help',
+  LOAD: 'load',
+  LOSECAPTURE: 'losecapture',
+  ORIENTATIONCHANGE: 'orientationchange',
+  READYSTATECHANGE: 'readystatechange',
+  RESIZE: 'resize',
+  SCROLL: 'scroll',
+  UNLOAD: 'unload',
+
+  // Media events
+  CANPLAY: 'canplay',
+  CANPLAYTHROUGH: 'canplaythrough',
+  DURATIONCHANGE: 'durationchange',
+  EMPTIED: 'emptied',
+  ENDED: 'ended',
+  LOADEDDATA: 'loadeddata',
+  LOADEDMETADATA: 'loadedmetadata',
+  PAUSE: 'pause',
+  PLAY: 'play',
+  PLAYING: 'playing',
+  PROGRESS: 'progress',
+  RATECHANGE: 'ratechange',
+  SEEKED: 'seeked',
+  SEEKING: 'seeking',
+  STALLED: 'stalled',
+  SUSPEND: 'suspend',
+  TIMEUPDATE: 'timeupdate',
+  VOLUMECHANGE: 'volumechange',
+  WAITING: 'waiting',
+
+  // Media Source Extensions events
+  // https://www.w3.org/TR/media-source/#mediasource-events
+  SOURCEOPEN: 'sourceopen',
+  SOURCEENDED: 'sourceended',
+  SOURCECLOSED: 'sourceclosed',
+  // https://www.w3.org/TR/media-source/#sourcebuffer-events
+  ABORT: 'abort',
+  UPDATE: 'update',
+  UPDATESTART: 'updatestart',
+  UPDATEEND: 'updateend',
+
+  // HTML 5 History events
+  // See http://www.w3.org/TR/html5/browsers.html#event-definitions-0
+  HASHCHANGE: 'hashchange',
+  PAGEHIDE: 'pagehide',
+  PAGESHOW: 'pageshow',
+  POPSTATE: 'popstate',
+
+  // Copy and Paste
+  // Support is limited. Make sure it works on your favorite browser
+  // before using.
+  // http://www.quirksmode.org/dom/events/cutcopypaste.html
+  COPY: 'copy',
+  PASTE: 'paste',
+  CUT: 'cut',
+  BEFORECOPY: 'beforecopy',
+  BEFORECUT: 'beforecut',
+  BEFOREPASTE: 'beforepaste',
+
+  // HTML5 online/offline events.
+  // http://www.w3.org/TR/offline-webapps/#related
+  ONLINE: 'online',
+  OFFLINE: 'offline',
+
+  // HTML 5 worker events
+  MESSAGE: 'message',
+  CONNECT: 'connect',
+
+  // Service Worker Events - ServiceWorkerGlobalScope context
+  // See https://w3c.github.io/ServiceWorker/#execution-context-events
+  // Note: message event defined in worker events section
+  INSTALL: 'install',
+  ACTIVATE: 'activate',
+  FETCH: 'fetch',
+  FOREIGNFETCH: 'foreignfetch',
+  MESSAGEERROR: 'messageerror',
+
+  // Service Worker Events - Document context
+  // See https://w3c.github.io/ServiceWorker/#document-context-events
+  STATECHANGE: 'statechange',
+  UPDATEFOUND: 'updatefound',
+  CONTROLLERCHANGE: 'controllerchange',
+
+  // CSS animation events.
+  ANIMATIONSTART: goog.events.getVendorPrefixedName_('AnimationStart'),
+  ANIMATIONEND: goog.events.getVendorPrefixedName_('AnimationEnd'),
+  ANIMATIONITERATION: goog.events.getVendorPrefixedName_('AnimationIteration'),
+
+  // CSS transition events. Based on the browser support described at:
+  // https://developer.mozilla.org/en/css/css_transitions#Browser_compatibility
+  TRANSITIONEND: goog.events.getVendorPrefixedName_('TransitionEnd'),
+
+  // W3C Pointer Events
+  // http://www.w3.org/TR/pointerevents/
+  POINTERDOWN: 'pointerdown',
+  POINTERUP: 'pointerup',
+  POINTERCANCEL: 'pointercancel',
+  POINTERMOVE: 'pointermove',
+  POINTEROVER: 'pointerover',
+  POINTEROUT: 'pointerout',
+  POINTERENTER: 'pointerenter',
+  POINTERLEAVE: 'pointerleave',
+  GOTPOINTERCAPTURE: 'gotpointercapture',
+  LOSTPOINTERCAPTURE: 'lostpointercapture',
+
+  // IE specific events.
+  // See http://msdn.microsoft.com/en-us/library/ie/hh772103(v=vs.85).aspx
+  // Note: these events will be supplanted in IE11.
+  MSGESTURECHANGE: 'MSGestureChange',
+  MSGESTUREEND: 'MSGestureEnd',
+  MSGESTUREHOLD: 'MSGestureHold',
+  MSGESTURESTART: 'MSGestureStart',
+  MSGESTURETAP: 'MSGestureTap',
+  MSGOTPOINTERCAPTURE: 'MSGotPointerCapture',
+  MSINERTIASTART: 'MSInertiaStart',
+  MSLOSTPOINTERCAPTURE: 'MSLostPointerCapture',
+  MSPOINTERCANCEL: 'MSPointerCancel',
+  MSPOINTERDOWN: 'MSPointerDown',
+  MSPOINTERENTER: 'MSPointerEnter',
+  MSPOINTERHOVER: 'MSPointerHover',
+  MSPOINTERLEAVE: 'MSPointerLeave',
+  MSPOINTERMOVE: 'MSPointerMove',
+  MSPOINTEROUT: 'MSPointerOut',
+  MSPOINTEROVER: 'MSPointerOver',
+  MSPOINTERUP: 'MSPointerUp',
+
+  // Native IMEs/input tools events.
+  TEXT: 'text',
+  // The textInput event is supported in IE9+, but only in lower case. All other
+  // browsers use the camel-case event name.
+  TEXTINPUT: goog.userAgent.IE ? 'textinput' : 'textInput',
+  COMPOSITIONSTART: 'compositionstart',
+  COMPOSITIONUPDATE: 'compositionupdate',
+  COMPOSITIONEND: 'compositionend',
+
+  // The beforeinput event is initially only supported in Safari. See
+  // https://bugs.chromium.org/p/chromium/issues/detail?id=342670 for Chrome
+  // implementation tracking.
+  BEFOREINPUT: 'beforeinput',
+
+  // Webview tag events
+  // See https://developer.chrome.com/apps/tags/webview
+  EXIT: 'exit',
+  LOADABORT: 'loadabort',
+  LOADCOMMIT: 'loadcommit',
+  LOADREDIRECT: 'loadredirect',
+  LOADSTART: 'loadstart',
+  LOADSTOP: 'loadstop',
+  RESPONSIVE: 'responsive',
+  SIZECHANGED: 'sizechanged',
+  UNRESPONSIVE: 'unresponsive',
+
+  // HTML5 Page Visibility API.  See details at
+  // `goog.labs.dom.PageVisibilityMonitor`.
+  VISIBILITYCHANGE: 'visibilitychange',
+
+  // LocalStorage event.
+  STORAGE: 'storage',
+
+  // DOM Level 2 mutation events (deprecated).
+  DOMSUBTREEMODIFIED: 'DOMSubtreeModified',
+  DOMNODEINSERTED: 'DOMNodeInserted',
+  DOMNODEREMOVED: 'DOMNodeRemoved',
+  DOMNODEREMOVEDFROMDOCUMENT: 'DOMNodeRemovedFromDocument',
+  DOMNODEINSERTEDINTODOCUMENT: 'DOMNodeInsertedIntoDocument',
+  DOMATTRMODIFIED: 'DOMAttrModified',
+  DOMCHARACTERDATAMODIFIED: 'DOMCharacterDataModified',
+
+  // Print events.
+  BEFOREPRINT: 'beforeprint',
+  AFTERPRINT: 'afterprint',
+
+  // Web app manifest events.
+  BEFOREINSTALLPROMPT: 'beforeinstallprompt',
+  APPINSTALLED: 'appinstalled'
+};
+
+
+/**
+ * Returns one of the given pointer fallback event names in order of preference:
+ *   1. pointerEventName
+ *   2. msPointerEventName
+ *   3. fallbackEventName
+ * @param {string} pointerEventName
+ * @param {string} msPointerEventName
+ * @param {string} fallbackEventName
+ * @return {string} The supported pointer or fallback (mouse or touch) event
+ *     name.
+ * @private
+ */
+goog.events.getPointerFallbackEventName_ = function(
+    pointerEventName, msPointerEventName, fallbackEventName) {
+  'use strict';
+  if (goog.events.BrowserFeature.POINTER_EVENTS) {
+    return pointerEventName;
+  }
+  if (goog.events.BrowserFeature.MSPOINTER_EVENTS) {
+    return msPointerEventName;
+  }
+  return fallbackEventName;
+};
+
+
+/**
+ * Constants for pointer event names that fall back to corresponding mouse event
+ * names on unsupported platforms. These are intended to be drop-in replacements
+ * for corresponding values in `goog.events.EventType`.
+ * @enum {string}
+ */
+goog.events.PointerFallbackEventType = {
+  POINTERDOWN: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERDOWN, goog.events.EventType.MSPOINTERDOWN,
+      goog.events.EventType.MOUSEDOWN),
+  POINTERUP: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERUP, goog.events.EventType.MSPOINTERUP,
+      goog.events.EventType.MOUSEUP),
+  POINTERCANCEL: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERCANCEL,
+      goog.events.EventType.MSPOINTERCANCEL,
+      // When falling back to mouse events, there is no MOUSECANCEL equivalent
+      // of POINTERCANCEL. In this case POINTERUP already falls back to MOUSEUP
+      // which represents both UP and CANCEL. POINTERCANCEL does not fall back
+      // to MOUSEUP to prevent listening twice on the same event.
+      goog.events.EventType.MOUSECANCEL),
+  POINTERMOVE: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERMOVE, goog.events.EventType.MSPOINTERMOVE,
+      goog.events.EventType.MOUSEMOVE),
+  POINTEROVER: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTEROVER, goog.events.EventType.MSPOINTEROVER,
+      goog.events.EventType.MOUSEOVER),
+  POINTEROUT: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTEROUT, goog.events.EventType.MSPOINTEROUT,
+      goog.events.EventType.MOUSEOUT),
+  POINTERENTER: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERENTER, goog.events.EventType.MSPOINTERENTER,
+      goog.events.EventType.MOUSEENTER),
+  POINTERLEAVE: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERLEAVE, goog.events.EventType.MSPOINTERLEAVE,
+      goog.events.EventType.MOUSELEAVE)
+};
+
+
+/**
+ * Constants for pointer event names that fall back to corresponding touch event
+ * names on unsupported platforms. These are intended to be drop-in replacements
+ * for corresponding values in `goog.events.EventType`.
+ * @enum {string}
+ */
+goog.events.PointerTouchFallbackEventType = {
+  POINTERDOWN: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERDOWN, goog.events.EventType.MSPOINTERDOWN,
+      goog.events.EventType.TOUCHSTART),
+  POINTERUP: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERUP, goog.events.EventType.MSPOINTERUP,
+      goog.events.EventType.TOUCHEND),
+  POINTERCANCEL: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERCANCEL,
+      goog.events.EventType.MSPOINTERCANCEL, goog.events.EventType.TOUCHCANCEL),
+  POINTERMOVE: goog.events.getPointerFallbackEventName_(
+      goog.events.EventType.POINTERMOVE, goog.events.EventType.MSPOINTERMOVE,
+      goog.events.EventType.TOUCHMOVE)
+};
+
+
+/**
+ * Mapping of mouse event names to underlying browser event names.
+ * @typedef {{
+ *     MOUSEDOWN: string,
+ *     MOUSEUP: string,
+ *     MOUSECANCEL:string,
+ *     MOUSEMOVE:string,
+ *     MOUSEOVER:string,
+ *     MOUSEOUT:string,
+ *     MOUSEENTER:string,
+ *     MOUSELEAVE: string,
+ * }}
+ */
+goog.events.MouseEvents;
+
+
+/**
+ * An alias for `goog.events.EventType.MOUSE*` event types that is overridden by
+ * corresponding `POINTER*` event types.
+ * @const {!goog.events.MouseEvents}
+ */
+goog.events.PointerAsMouseEventType = {
+  MOUSEDOWN: goog.events.PointerFallbackEventType.POINTERDOWN,
+  MOUSEUP: goog.events.PointerFallbackEventType.POINTERUP,
+  MOUSECANCEL: goog.events.PointerFallbackEventType.POINTERCANCEL,
+  MOUSEMOVE: goog.events.PointerFallbackEventType.POINTERMOVE,
+  MOUSEOVER: goog.events.PointerFallbackEventType.POINTEROVER,
+  MOUSEOUT: goog.events.PointerFallbackEventType.POINTEROUT,
+  MOUSEENTER: goog.events.PointerFallbackEventType.POINTERENTER,
+  MOUSELEAVE: goog.events.PointerFallbackEventType.POINTERLEAVE
+};
+
+
+/**
+ * An alias for `goog.events.EventType.MOUSE*` event types that continue to use
+ * mouse events.
+ * @const {!goog.events.MouseEvents}
+ */
+goog.events.MouseAsMouseEventType = {
+  MOUSEDOWN: goog.events.EventType.MOUSEDOWN,
+  MOUSEUP: goog.events.EventType.MOUSEUP,
+  MOUSECANCEL: goog.events.EventType.MOUSECANCEL,
+  MOUSEMOVE: goog.events.EventType.MOUSEMOVE,
+  MOUSEOVER: goog.events.EventType.MOUSEOVER,
+  MOUSEOUT: goog.events.EventType.MOUSEOUT,
+  MOUSEENTER: goog.events.EventType.MOUSEENTER,
+  MOUSELEAVE: goog.events.EventType.MOUSELEAVE
+};
+
+
+/**
+ * An alias for `goog.events.EventType.TOUCH*` event types that is overridden by
+ * corresponding `POINTER*` event types.
+ * @enum {string}
+ */
+goog.events.PointerAsTouchEventType = {
+  TOUCHCANCEL: goog.events.PointerTouchFallbackEventType.POINTERCANCEL,
+  TOUCHEND: goog.events.PointerTouchFallbackEventType.POINTERUP,
+  TOUCHMOVE: goog.events.PointerTouchFallbackEventType.POINTERMOVE,
+  TOUCHSTART: goog.events.PointerTouchFallbackEventType.POINTERDOWN
+};

js/goog/events/eventwrapper.js

@@ -0,0 +1,56 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Definition of the goog.events.EventWrapper interface.
+ */
+
+goog.provide('goog.events.EventWrapper');
+
+goog.requireType('goog.events.EventHandler');
+goog.requireType('goog.events.ListenableType');
+
+
+
+/**
+ * Interface for event wrappers.
+ * @interface
+ */
+goog.events.EventWrapper = function() {};
+
+
+/**
+ * Adds an event listener using the wrapper on a DOM Node or an object that has
+ * implemented {@link goog.events.EventTarget}. A listener can only be added
+ * once to an object.
+ *
+ * @param {goog.events.ListenableType} src The node to listen to events on.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener Callback
+ *     method, or an object with a handleEvent function.
+ * @param {boolean=} opt_capt Whether to fire in capture phase (defaults to
+ *     false).
+ * @param {Object=} opt_scope Element in whose scope to call the listener.
+ * @param {goog.events.EventHandler=} opt_eventHandler Event handler to add
+ *     listener to.
+ */
+goog.events.EventWrapper.prototype.listen = function(
+    src, listener, opt_capt, opt_scope, opt_eventHandler) {};
+
+
+/**
+ * Removes an event listener added using goog.events.EventWrapper.listen.
+ *
+ * @param {goog.events.ListenableType} src The node to remove listener from.
+ * @param {function(?):?|{handleEvent:function(?):?}|null} listener Callback
+ *     method, or an object with a handleEvent function.
+ * @param {boolean=} opt_capt Whether to fire in capture phase (defaults to
+ *     false).
+ * @param {Object=} opt_scope Element in whose scope to call the listener.
+ * @param {goog.events.EventHandler=} opt_eventHandler Event handler to remove
+ *     listener from.
+ */
+goog.events.EventWrapper.prototype.unlisten = function(
+    src, listener, opt_capt, opt_scope, opt_eventHandler) {};

js/goog/events/listenable.js

@@ -0,0 +1,265 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview An interface for a listenable JavaScript object.
+ */
+
+goog.provide('goog.events.Listenable');
+
+goog.requireType('goog.events.EventId');
+goog.requireType('goog.events.EventLike');
+goog.requireType('goog.events.ListenableKey');
+
+
+/**
+ * A listenable interface. A listenable is an object with the ability
+ * to dispatch/broadcast events to "event listeners" registered via
+ * listen/listenOnce.
+ *
+ * The interface allows for an event propagation mechanism similar
+ * to one offered by native browser event targets, such as
+ * capture/bubble mechanism, stopping propagation, and preventing
+ * default actions. Capture/bubble mechanism depends on the ancestor
+ * tree constructed via `#getParentEventTarget`; this tree
+ * must be directed acyclic graph. The meaning of default action(s)
+ * in preventDefault is specific to a particular use case.
+ *
+ * Implementations that do not support capture/bubble or can not have
+ * a parent listenable can simply not implement any ability to set the
+ * parent listenable (and have `#getParentEventTarget` return
+ * null).
+ *
+ * Implementation of this class can be used with or independently from
+ * goog.events.
+ *
+ * Implementation must call `#addImplementation(implClass)`.
+ *
+ * @interface
+ * @see goog.events
+ * @see http://www.w3.org/TR/DOM-Level-2-Events/events.html
+ */
+goog.events.Listenable = function() {};
+
+
+/**
+ * An expando property to indicate that an object implements
+ * goog.events.Listenable.
+ *
+ * See addImplementation/isImplementedBy.
+ *
+ * @type {string}
+ * @const
+ */
+goog.events.Listenable.IMPLEMENTED_BY_PROP =
+    'closure_listenable_' + ((Math.random() * 1e6) | 0);
+
+
+/**
+ * Marks a given class (constructor) as an implementation of
+ * Listenable, so that we can query that fact at runtime. The class
+ * must have already implemented the interface.
+ * @param {function(new:goog.events.Listenable,...)} cls The class constructor.
+ *     The corresponding class must have already implemented the interface.
+ */
+goog.events.Listenable.addImplementation = function(cls) {
+  'use strict';
+  cls.prototype[goog.events.Listenable.IMPLEMENTED_BY_PROP] = true;
+};
+
+
+/**
+ * @param {?Object} obj The object to check.
+ * @return {boolean} Whether a given instance implements Listenable. The
+ *     class/superclass of the instance must call addImplementation.
+ */
+goog.events.Listenable.isImplementedBy = function(obj) {
+  'use strict';
+  return !!(obj && obj[goog.events.Listenable.IMPLEMENTED_BY_PROP]);
+};
+
+
+/**
+ * Adds an event listener. A listener can only be added once to an
+ * object and if it is added again the key for the listener is
+ * returned. Note that if the existing listener is a one-off listener
+ * (registered via listenOnce), it will no longer be a one-off
+ * listener after a call to listen().
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {!goog.events.ListenableKey} Unique key for the listener.
+ * @template SCOPE,EVENTOBJ
+ */
+goog.events.Listenable.prototype.listen = function(
+    type, listener, opt_useCapture, opt_listenerScope) {};
+
+
+/**
+ * Adds an event listener that is removed automatically after the
+ * listener fired once.
+ *
+ * If an existing listener already exists, listenOnce will do
+ * nothing. In particular, if the listener was previously registered
+ * via listen(), listenOnce() will not turn the listener into a
+ * one-off listener. Similarly, if there is already an existing
+ * one-off listener, listenOnce does not modify the listeners (it is
+ * still a once listener).
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {!goog.events.ListenableKey} Unique key for the listener.
+ * @template SCOPE,EVENTOBJ
+ */
+goog.events.Listenable.prototype.listenOnce = function(
+    type, listener, opt_useCapture, opt_listenerScope) {};
+
+
+/**
+ * Removes an event listener which was added with listen() or listenOnce().
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The event type id.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener Callback
+ *     method.
+ * @param {boolean=} opt_useCapture Whether to fire in capture phase
+ *     (defaults to false).
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call
+ *     the listener.
+ * @return {boolean} Whether any listener was removed.
+ * @template SCOPE,EVENTOBJ
+ */
+goog.events.Listenable.prototype.unlisten = function(
+    type, listener, opt_useCapture, opt_listenerScope) {};
+
+
+/**
+ * Removes an event listener which was added with listen() by the key
+ * returned by listen().
+ *
+ * @param {!goog.events.ListenableKey} key The key returned by
+ *     listen() or listenOnce().
+ * @return {boolean} Whether any listener was removed.
+ */
+goog.events.Listenable.prototype.unlistenByKey = function(key) {};
+
+
+/**
+ * Dispatches an event (or event like object) and calls all listeners
+ * listening for events of this type. The type of the event is decided by the
+ * type property on the event object.
+ *
+ * If any of the listeners returns false OR calls preventDefault then this
+ * function will return false.  If one of the capture listeners calls
+ * stopPropagation, then the bubble listeners won't fire.
+ *
+ * @param {?goog.events.EventLike} e Event object.
+ * @return {boolean} If anyone called preventDefault on the event object (or
+ *     if any of the listeners returns false) this will also return false.
+ */
+goog.events.Listenable.prototype.dispatchEvent = function(e) {};
+
+
+/**
+ * Removes all listeners from this listenable. If type is specified,
+ * it will only remove listeners of the particular type. otherwise all
+ * registered listeners will be removed.
+ *
+ * @param {string|!goog.events.EventId=} opt_type Type of event to remove,
+ *     default is to remove all types.
+ * @return {number} Number of listeners removed.
+ */
+goog.events.Listenable.prototype.removeAllListeners = function(opt_type) {};
+
+
+/**
+ * Returns the parent of this event target to use for capture/bubble
+ * mechanism.
+ *
+ * NOTE(chrishenry): The name reflects the original implementation of
+ * custom event target (`goog.events.EventTarget`). We decided
+ * that changing the name is not worth it.
+ *
+ * @return {?goog.events.Listenable} The parent EventTarget or null if
+ *     there is no parent.
+ */
+goog.events.Listenable.prototype.getParentEventTarget = function() {};
+
+
+/**
+ * Fires all registered listeners in this listenable for the given
+ * type and capture mode, passing them the given eventObject. This
+ * does not perform actual capture/bubble. Only implementors of the
+ * interface should be using this.
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The type of the
+ *     listeners to fire.
+ * @param {boolean} capture The capture mode of the listeners to fire.
+ * @param {EVENTOBJ} eventObject The event object to fire.
+ * @return {boolean} Whether all listeners succeeded without
+ *     attempting to prevent default behavior. If any listener returns
+ *     false or called goog.events.Event#preventDefault, this returns
+ *     false.
+ * @template EVENTOBJ
+ */
+goog.events.Listenable.prototype.fireListeners = function(
+    type, capture, eventObject) {};
+
+
+/**
+ * Gets all listeners in this listenable for the given type and
+ * capture mode.
+ *
+ * @param {string|!goog.events.EventId} type The type of the listeners to fire.
+ * @param {boolean} capture The capture mode of the listeners to fire.
+ * @return {!Array<!goog.events.ListenableKey>} An array of registered
+ *     listeners.
+ * @template EVENTOBJ
+ */
+goog.events.Listenable.prototype.getListeners = function(type, capture) {};
+
+
+/**
+ * Gets the goog.events.ListenableKey for the event or null if no such
+ * listener is in use.
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>} type The name of the event
+ *     without the 'on' prefix.
+ * @param {function(this:SCOPE, EVENTOBJ):(boolean|undefined)} listener The
+ *     listener function to get.
+ * @param {boolean} capture Whether the listener is a capturing listener.
+ * @param {SCOPE=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {?goog.events.ListenableKey} the found listener or null if not found.
+ * @template SCOPE,EVENTOBJ
+ */
+goog.events.Listenable.prototype.getListener = function(
+    type, listener, capture, opt_listenerScope) {};
+
+
+/**
+ * Whether there is any active listeners matching the specified
+ * signature. If either the type or capture parameters are
+ * unspecified, the function will match on the remaining criteria.
+ *
+ * @param {string|!goog.events.EventId<EVENTOBJ>=} opt_type Event type.
+ * @param {boolean=} opt_capture Whether to check for capture or bubble
+ *     listeners.
+ * @return {boolean} Whether there is any active listeners matching
+ *     the requested type and/or capture phase.
+ * @template EVENTOBJ
+ */
+goog.events.Listenable.prototype.hasListener = function(
+    opt_type, opt_capture) {};

js/goog/events/listenablekey.js

@@ -0,0 +1,80 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview An interface that describes a single registered listener.
+ */
+goog.provide('goog.events.ListenableKey');
+
+goog.requireType('goog.events.Listenable');
+
+
+/**
+ * An interface that describes a single registered listener.
+ * @interface
+ */
+goog.events.ListenableKey = function() {};
+
+
+/**
+ * Counter used to create a unique key
+ * @type {number}
+ * @private
+ */
+goog.events.ListenableKey.counter_ = 0;
+
+
+/**
+ * Reserves a key to be used for ListenableKey#key field.
+ * @return {number} A number to be used to fill ListenableKey#key
+ *     field.
+ */
+goog.events.ListenableKey.reserveKey = function() {
+  'use strict';
+  return ++goog.events.ListenableKey.counter_;
+};
+
+
+/**
+ * The source event target.
+ * @type {?Object|?goog.events.Listenable}
+ */
+goog.events.ListenableKey.prototype.src;
+
+
+/**
+ * The event type the listener is listening to.
+ * @type {string}
+ */
+goog.events.ListenableKey.prototype.type;
+
+
+/**
+ * The listener function.
+ * @type {function(?):?|{handleEvent:function(?):?}|null}
+ */
+goog.events.ListenableKey.prototype.listener;
+
+
+/**
+ * Whether the listener works on capture phase.
+ * @type {boolean}
+ */
+goog.events.ListenableKey.prototype.capture;
+
+
+/**
+ * The 'this' object for the listener function's scope.
+ * @type {?Object|undefined}
+ */
+goog.events.ListenableKey.prototype.handler;
+
+
+/**
+ * A globally unique number to identify the key.
+ * @type {number}
+ */
+goog.events.ListenableKey.prototype.key;

js/goog/events/listener.js

@@ -0,0 +1,124 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Listener object.
+ * @see ../demos/events.html
+ */
+
+goog.provide('goog.events.Listener');
+
+goog.require('goog.events.ListenableKey');
+goog.requireType('goog.events.Listenable');
+
+
+
+/**
+ * Simple class that stores information about a listener
+ * @param {function(?):?} listener Callback function.
+ * @param {Function} proxy Wrapper for the listener that patches the event.
+ * @param {EventTarget|goog.events.Listenable} src Source object for
+ *     the event.
+ * @param {string} type Event type.
+ * @param {boolean} capture Whether in capture or bubble phase.
+ * @param {Object=} opt_handler Object in whose context to execute the callback.
+ * @implements {goog.events.ListenableKey}
+ * @constructor
+ */
+goog.events.Listener = function(
+    listener, proxy, src, type, capture, opt_handler) {
+  'use strict';
+  if (goog.events.Listener.ENABLE_MONITORING) {
+    this.creationStack = new Error().stack;
+  }
+
+  /** @override */
+  this.listener = listener;
+
+  /**
+   * A wrapper over the original listener. This is used solely to
+   * handle native browser events (it is used to simulate the capture
+   * phase and to patch the event object).
+   * @type {Function}
+   */
+  this.proxy = proxy;
+
+  /**
+   * Object or node that callback is listening to
+   * @type {EventTarget|goog.events.Listenable}
+   */
+  this.src = src;
+
+  /**
+   * The event type.
+   * @const {string}
+   */
+  this.type = type;
+
+  /**
+   * Whether the listener is being called in the capture or bubble phase
+   * @const {boolean}
+   */
+  this.capture = !!capture;
+
+  /**
+   * Optional object whose context to execute the listener in
+   * @type {Object|undefined}
+   */
+  this.handler = opt_handler;
+
+  /**
+   * The key of the listener.
+   * @const {number}
+   * @override
+   */
+  this.key = goog.events.ListenableKey.reserveKey();
+
+  /**
+   * Whether to remove the listener after it has been called.
+   * @type {boolean}
+   */
+  this.callOnce = false;
+
+  /**
+   * Whether the listener has been removed.
+   * @type {boolean}
+   */
+  this.removed = false;
+};
+
+
+/**
+ * @define {boolean} Whether to enable the monitoring of the
+ *     goog.events.Listener instances. Switching on the monitoring is only
+ *     recommended for debugging because it has a significant impact on
+ *     performance and memory usage. If switched off, the monitoring code
+ *     compiles down to 0 bytes.
+ */
+goog.events.Listener.ENABLE_MONITORING =
+    goog.define('goog.events.Listener.ENABLE_MONITORING', false);
+
+
+/**
+ * If monitoring the goog.events.Listener instances is enabled, stores the
+ * creation stack trace of the Disposable instance.
+ * @type {string}
+ */
+goog.events.Listener.prototype.creationStack;
+
+
+/**
+ * Marks this listener as removed. This also remove references held by
+ * this listener object (such as listener and event source).
+ */
+goog.events.Listener.prototype.markAsRemoved = function() {
+  'use strict';
+  this.removed = true;
+  this.listener = null;
+  this.proxy = null;
+  this.src = null;
+  this.handler = null;
+};

js/goog/events/listenermap.js

@@ -0,0 +1,310 @@
+/**
+ * @license
+ * Copyright The Closure Library Authors.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview A map of listeners that provides utility functions to
+ * deal with listeners on an event target. Used by
+ * `goog.events.EventTarget`.
+ *
+ * WARNING: Do not use this class from outside goog.events package.
+ *
+ */
+
+goog.provide('goog.events.ListenerMap');
+
+goog.require('goog.array');
+goog.require('goog.events.Listener');
+goog.require('goog.object');
+goog.requireType('goog.events.EventId');
+goog.requireType('goog.events.Listenable');
+goog.requireType('goog.events.ListenableKey');
+
+
+
+/**
+ * Creates a new listener map.
+ * @param {EventTarget|goog.events.Listenable} src The src object.
+ * @constructor
+ * @final
+ */
+goog.events.ListenerMap = function(src) {
+  'use strict';
+  /** @type {EventTarget|goog.events.Listenable} */
+  this.src = src;
+
+  /**
+   * Maps of event type to an array of listeners.
+   * @type {!Object<string, !Array<!goog.events.Listener>>}
+   */
+  this.listeners = {};
+
+  /**
+   * The count of types in this map that have registered listeners.
+   * @private {number}
+   */
+  this.typeCount_ = 0;
+};
+
+
+/**
+ * @return {number} The count of event types in this map that actually
+ *     have registered listeners.
+ */
+goog.events.ListenerMap.prototype.getTypeCount = function() {
+  'use strict';
+  return this.typeCount_;
+};
+
+
+/**
+ * @return {number} Total number of registered listeners.
+ */
+goog.events.ListenerMap.prototype.getListenerCount = function() {
+  'use strict';
+  var count = 0;
+  for (var type in this.listeners) {
+    count += this.listeners[type].length;
+  }
+  return count;
+};
+
+
+/**
+ * Adds an event listener. A listener can only be added once to an
+ * object and if it is added again the key for the listener is
+ * returned.
+ *
+ * Note that a one-off listener will not change an existing listener,
+ * if any. On the other hand a normal listener will change existing
+ * one-off listener to become a normal listener.
+ *
+ * @param {string|!goog.events.EventId} type The listener event type.
+ * @param {!Function} listener This listener callback method.
+ * @param {boolean} callOnce Whether the listener is a one-off
+ *     listener.
+ * @param {boolean=} opt_useCapture The capture mode of the listener.
+ * @param {Object=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {!goog.events.ListenableKey} Unique key for the listener.
+ */
+goog.events.ListenerMap.prototype.add = function(
+    type, listener, callOnce, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  var typeStr = type.toString();
+  var listenerArray = this.listeners[typeStr];
+  if (!listenerArray) {
+    listenerArray = this.listeners[typeStr] = [];
+    this.typeCount_++;
+  }
+
+  var listenerObj;
+  var index = goog.events.ListenerMap.findListenerIndex_(
+      listenerArray, listener, opt_useCapture, opt_listenerScope);
+  if (index > -1) {
+    listenerObj = listenerArray[index];
+    if (!callOnce) {
+      // Ensure that, if there is an existing callOnce listener, it is no
+      // longer a callOnce listener.
+      listenerObj.callOnce = false;
+    }
+  } else {
+    listenerObj = new goog.events.Listener(
+        listener, null, this.src, typeStr, !!opt_useCapture, opt_listenerScope);
+    listenerObj.callOnce = callOnce;
+    listenerArray.push(listenerObj);
+  }
+  return listenerObj;
+};
+
+
+/**
+ * Removes a matching listener.
+ * @param {string|!goog.events.EventId} type The listener event type.
+ * @param {!Function} listener This listener callback method.
+ * @param {boolean=} opt_useCapture The capture mode of the listener.
+ * @param {Object=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {boolean} Whether any listener was removed.
+ */
+goog.events.ListenerMap.prototype.remove = function(
+    type, listener, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  var typeStr = type.toString();
+  if (!(typeStr in this.listeners)) {
+    return false;
+  }
+
+  var listenerArray = this.listeners[typeStr];
+  var index = goog.events.ListenerMap.findListenerIndex_(
+      listenerArray, listener, opt_useCapture, opt_listenerScope);
+  if (index > -1) {
+    var listenerObj = listenerArray[index];
+    listenerObj.markAsRemoved();
+    goog.array.removeAt(listenerArray, index);
+    if (listenerArray.length == 0) {
+      delete this.listeners[typeStr];
+      this.typeCount_--;
+    }
+    return true;
+  }
+  return false;
+};
+
+
+/**
+ * Removes the given listener object.
+ * @param {!goog.events.ListenableKey} listener The listener to remove.
+ * @return {boolean} Whether the listener is removed.
+ */
+goog.events.ListenerMap.prototype.removeByKey = function(listener) {
+  'use strict';
+  var type = listener.type;
+  if (!(type in this.listeners)) {
+    return false;
+  }
+
+  var removed = goog.array.remove(this.listeners[type], listener);
+  if (removed) {
+    /** @type {!goog.events.Listener} */ (listener).markAsRemoved();
+    if (this.listeners[type].length == 0) {
+      delete this.listeners[type];
+      this.typeCount_--;
+    }
+  }
+  return removed;
+};
+
+
+/**
+ * Removes all listeners from this map. If opt_type is provided, only
+ * listeners that match the given type are removed.
+ * @param {string|!goog.events.EventId=} opt_type Type of event to remove.
+ * @return {number} Number of listeners removed.
+ */
+goog.events.ListenerMap.prototype.removeAll = function(opt_type) {
+  'use strict';
+  var typeStr = opt_type && opt_type.toString();
+  var count = 0;
+  for (var type in this.listeners) {
+    if (!typeStr || type == typeStr) {
+      var listenerArray = this.listeners[type];
+      for (var i = 0; i < listenerArray.length; i++) {
+        ++count;
+        listenerArray[i].markAsRemoved();
+      }
+      delete this.listeners[type];
+      this.typeCount_--;
+    }
+  }
+  return count;
+};
+
+
+/**
+ * Gets all listeners that match the given type and capture mode. The
+ * returned array is a copy (but the listener objects are not).
+ * @param {string|!goog.events.EventId} type The type of the listeners
+ *     to retrieve.
+ * @param {boolean} capture The capture mode of the listeners to retrieve.
+ * @return {!Array<!goog.events.ListenableKey>} An array of matching
+ *     listeners.
+ */
+goog.events.ListenerMap.prototype.getListeners = function(type, capture) {
+  'use strict';
+  var listenerArray = this.listeners[type.toString()];
+  var rv = [];
+  if (listenerArray) {
+    for (var i = 0; i < listenerArray.length; ++i) {
+      var listenerObj = listenerArray[i];
+      if (listenerObj.capture == capture) {
+        rv.push(listenerObj);
+      }
+    }
+  }
+  return rv;
+};
+
+
+/**
+ * Gets the goog.events.ListenableKey for the event or null if no such
+ * listener is in use.
+ *
+ * @param {string|!goog.events.EventId} type The type of the listener
+ *     to retrieve.
+ * @param {!Function} listener The listener function to get.
+ * @param {boolean} capture Whether the listener is a capturing listener.
+ * @param {Object=} opt_listenerScope Object in whose scope to call the
+ *     listener.
+ * @return {goog.events.ListenableKey} the found listener or null if not found.
+ */
+goog.events.ListenerMap.prototype.getListener = function(
+    type, listener, capture, opt_listenerScope) {
+  'use strict';
+  var listenerArray = this.listeners[type.toString()];
+  var i = -1;
+  if (listenerArray) {
+    i = goog.events.ListenerMap.findListenerIndex_(
+        listenerArray, listener, capture, opt_listenerScope);
+  }
+  return i > -1 ? listenerArray[i] : null;
+};
+
+
+/**
+ * Whether there is a matching listener. If either the type or capture
+ * parameters are unspecified, the function will match on the
+ * remaining criteria.
+ *
+ * @param {string|!goog.events.EventId=} opt_type The type of the listener.
+ * @param {boolean=} opt_capture The capture mode of the listener.
+ * @return {boolean} Whether there is an active listener matching
+ *     the requested type and/or capture phase.
+ */
+goog.events.ListenerMap.prototype.hasListener = function(
+    opt_type, opt_capture) {
+  'use strict';
+  var hasType = (opt_type !== undefined);
+  var typeStr = hasType ? opt_type.toString() : '';
+  var hasCapture = (opt_capture !== undefined);
+
+  return goog.object.some(this.listeners, function(listenerArray, type) {
+    'use strict';
+    for (var i = 0; i < listenerArray.length; ++i) {
+      if ((!hasType || listenerArray[i].type == typeStr) &&
+          (!hasCapture || listenerArray[i].capture == opt_capture)) {
+        return true;
+      }
+    }
+
+    return false;
+  });
+};
+
+
+/**
+ * Finds the index of a matching goog.events.Listener in the given
+ * listenerArray.
+ * @param {!Array<!goog.events.Listener>} listenerArray Array of listener.
+ * @param {!Function} listener The listener function.
+ * @param {boolean=} opt_useCapture The capture flag for the listener.
+ * @param {Object=} opt_listenerScope The listener scope.
+ * @return {number} The index of the matching listener within the
+ *     listenerArray.
+ * @private
+ */
+goog.events.ListenerMap.findListenerIndex_ = function(
+    listenerArray, listener, opt_useCapture, opt_listenerScope) {
+  'use strict';
+  for (var i = 0; i < listenerArray.length; ++i) {
+    var listenerObj = listenerArray[i];
+    if (!listenerObj.removed && listenerObj.listener == listener &&
+        listenerObj.capture == !!opt_useCapture &&
+        listenerObj.handler == opt_listenerScope) {
+      return i;
+    }
+  }
+  return -1;
+};