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

third_party/WebKit/Source/devtools/front_end/ui/ZoomManager.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.Object}
  * @param {!Window} window
  * @param {!InspectorFrontendHostAPI} frontendHost
  */
 WebInspector.ZoomManager = function(window, frontendHost)
 {
     this._frontendHost = frontendHost;
     this._zoomFactor = this._frontendHost.zoomFactor();
     window.addEventListener("resize", this._onWindowResize.bind(this), true);
 };
 
+/** @enum {symbol} */
 WebInspector.ZoomManager.Events = {
-    ZoomChanged: "ZoomChanged"
+    ZoomChanged: Symbol("ZoomChanged")
 };
 
 WebInspector.ZoomManager.prototype = {
     /**
      * @return {number}
      */
     zoomFactor: function()
     {
         return this._zoomFactor;
     },
@@ skipping 24 matching lines @@
             this.dispatchEventToListeners(WebInspector.ZoomManager.Events.ZoomChanged, {from: oldZoomFactor, to: this._zoomFactor});
     },
 
     __proto__: WebInspector.Object.prototype
 };
 
 /**
  * @type {!WebInspector.ZoomManager}
  */
 WebInspector.zoomManager;