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

third_party/WebKit/Source/devtools/front_end/sdk/NetworkManager.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 715 matching lines @@
     this._blockedSetting.set([]);
     this._updateBlockedURLs();
 
     this._userAgentOverride = "";
     /** @type {!Set<!Protocol.NetworkAgent>} */
     this._agents = new Set();
     /** @type {!WebInspector.NetworkManager.Conditions} */
     this._networkConditions = WebInspector.NetworkManager.NoThrottlingConditions;
 }
 
+/** @enum {symbol} */
 WebInspector.MultitargetNetworkManager.Events = {
-    ConditionsChanged: "ConditionsChanged",
-    UserAgentChanged: "UserAgentChanged"
+    ConditionsChanged: Symbol("ConditionsChanged"),
+    UserAgentChanged: Symbol("UserAgentChanged")
 }
 
 WebInspector.MultitargetNetworkManager.prototype = {
     /**
      * @override
      * @param {!WebInspector.Target} target
      */
     targetAdded: function(target)
     {
         var networkAgent = target.networkAgent();
@@ skipping 194 matching lines @@
         WebInspector.ResourceLoader.load(url, headers, callback);
     },
 
     __proto__: WebInspector.Object.prototype
 }
 
 /**
  * @type {!WebInspector.MultitargetNetworkManager}
  */
 WebInspector.multitargetNetworkManager;