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

third_party/WebKit/Source/devtools/front_end/ui_lazy/FlameChart.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 304 matching lines @@
 
     /**
      * @param {!CanvasRenderingContext2D} context
      * @param {number} x
      * @param {number} height
      * @param {number} pixelsPerMillisecond
      */
     draw: function(context, x, height, pixelsPerMillisecond) { },
 }
 
+/** @enum {symbol} */
 WebInspector.FlameChart.Events = {
-    EntrySelected: "EntrySelected"
+    EntrySelected: Symbol("EntrySelected")
 }
 
 
 /**
  * @constructor
  * @param {!{min: number, max: number}|number=} hueSpace
  * @param {!{min: number, max: number, count: (number|undefined)}|number=} satSpace
  * @param {!{min: number, max: number, count: (number|undefined)}|number=} lightnessSpace
  * @param {!{min: number, max: number, count: (number|undefined)}|number=} alphaSpace
  */
@@ skipping 1682 matching lines @@
         this.update();
     },
 
     _enabled: function()
     {
         return this._rawTimelineDataLength !== 0;
     },
 
     __proto__: WebInspector.HBox.prototype
 }