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

third_party/WebKit/Source/devtools/front_end/sdk/TargetManager.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}
  */
 WebInspector.TargetManager = function()
 {
     WebInspector.Object.call(this);
     /** @type {!Array.<!WebInspector.Target>} */
     this._targets = [];
     /** @type {!Array.<!WebInspector.TargetManager.Observer>} */
     this._observers = [];
     this._observerCapabiliesMaskSymbol = Symbol("observerCapabilitiesMask");
     /** @type {!Object.<string, !Array.<{modelClass: !Function, thisObject: (!Object|undefined), listener: function(!WebInspector.Event)}>>} */
     this._modelListeners = {};
     this._isSuspended = false;
 }
 
+/** @enum {symbol} */
 WebInspector.TargetManager.Events = {
-    InspectedURLChanged: "InspectedURLChanged",
-    MainFrameNavigated: "MainFrameNavigated",
-    Load: "Load",
-    PageReloadRequested: "PageReloadRequested",
-    WillReloadPage: "WillReloadPage",
-    TargetDisposed: "TargetDisposed",
-    SuspendStateChanged: "SuspendStateChanged"
+    InspectedURLChanged: Symbol("InspectedURLChanged"),
+    MainFrameNavigated: Symbol("MainFrameNavigated"),
+    Load: Symbol("Load"),
+    PageReloadRequested: Symbol("PageReloadRequested"),
+    WillReloadPage: Symbol("WillReloadPage"),
+    TargetDisposed: Symbol("TargetDisposed"),
+    SuspendStateChanged: Symbol("SuspendStateChanged")
 }
 
 WebInspector.TargetManager.prototype = {
     suspendAllTargets: function()
     {
         if (this._isSuspended)
             return;
         this._isSuspended = true;
         this.dispatchEventToListeners(WebInspector.TargetManager.Events.SuspendStateChanged);
 
@@ skipping 311 matching lines @@
     /**
      * @param {!WebInspector.Target} target
      */
     targetRemoved: function(target) { },
 }
 
 /**
  * @type {!WebInspector.TargetManager}
  */
 WebInspector.targetManager = new WebInspector.TargetManager();