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

third_party/WebKit/Source/devtools/front_end/sdk/InspectorBackend.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 197 matching lines @@
 {
     this._lastMessageId = 1;
     this._pendingResponsesCount = 0;
     this._agents = {};
     this._dispatchers = {};
     this._callbacks = {};
     this._initialize(InspectorBackend._agentPrototypes, InspectorBackend._dispatcherPrototypes);
     this._isConnected = true;
 }
 
+/** @enum {symbol} */
 InspectorBackendClass.Connection.Events = {
-    Disconnected: "Disconnected",
+    Disconnected: Symbol("Disconnected")
 }
 
 InspectorBackendClass.Connection.prototype = {
     /**
      * @param {!Object.<string, !InspectorBackendClass.AgentPrototype>} agentPrototypes
      * @param {!Object.<string, !InspectorBackendClass.DispatcherPrototype>} dispatcherPrototypes
      */
     _initialize: function(agentPrototypes, dispatcherPrototypes)
     {
         for (var domain in agentPrototypes) {
@@ skipping 503 matching lines @@
     }
 }
 
 InspectorBackendClass.Options = {
     dumpInspectorTimeStats: false,
     dumpInspectorProtocolMessages: false,
     suppressRequestErrors: false
 }
 
 InspectorBackend = new InspectorBackendClass();