DevTools: Use JS symbols instead of strings for eligible events.

third_party/WebKit/Source/devtools/front_end/ui_lazy/TimelineOverviewPane.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 44 matching lines @@
     this._popoverHelper = new WebInspector.PopoverHelper(this._cursorArea, this._getPopoverAnchor.bind(this), this._showPopover.bind(this), this._onHidePopover.bind(this));
     this._popoverHelper.setTimeout(0);
 
     this._updateThrottler = new WebInspector.Throttler(100);
 
     this._cursorEnabled = false;
     this._cursorPosition = 0;
     this._lastWidth = 0;
 }
 
+/** @enum {symbol} */
 WebInspector.TimelineOverviewPane.Events = {
-    WindowChanged: "WindowChanged"
+    WindowChanged: Symbol("WindowChanged")
 };
 
 WebInspector.TimelineOverviewPane.prototype = {
     /**
      * @param {!Element} element
      * @param {!Event} event
      * @return {!Element|!AnchorBox|undefined}
      */
     _getPopoverAnchor: function(element, event)
     {
@@ skipping 555 matching lines @@
     },
 
     resetCanvas: function()
     {
         this._canvas.width = this.element.clientWidth * window.devicePixelRatio;
         this._canvas.height = this.element.clientHeight * window.devicePixelRatio;
     },
 
     __proto__: WebInspector.VBox.prototype
 }