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

third_party/WebKit/Source/devtools/front_end/profiler/HeapSnapshotGridNodes.js

 /*
  * Copyright (C) 2011 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 35 matching lines @@
      * Position is an item position in the provider.
      */
     this._retrievedChildrenRanges = [];
 
     /**
       * @type {?WebInspector.HeapSnapshotGridNode.ChildrenProvider}
       */
     this._providerObject = null;
 }
 
+/** @enum {symbol} */
 WebInspector.HeapSnapshotGridNode.Events = {
-    PopulateComplete: "PopulateComplete"
+    PopulateComplete: Symbol("PopulateComplete")
 }
 
 /**
  * @param {!Array.<string>} fieldNames
  * @return {!WebInspector.HeapSnapshotCommon.ComparatorConfig}
  */
 WebInspector.HeapSnapshotGridNode.createComparator = function(fieldNames)
 {
     return /** @type {!WebInspector.HeapSnapshotCommon.ComparatorConfig} */ ({fieldName1: fieldNames[0], ascending1: fieldNames[1], fieldName2: fieldNames[2], ascending2: fieldNames[3]});
 }
@@ skipping 1454 matching lines @@
     /**
      * @return {number}
      */
     allocationNodeId: function()
     {
         return this._allocationNode.id;
     },
 
     __proto__: WebInspector.HeapSnapshotGridNode.prototype
 }