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

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

 /*
  * Copyright (C) 2010 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 41 matching lines @@
     /** @type {!Array.<!WebInspector.TabbedPaneTab>} */
     this._tabsHistory = [];
     /** @type {!Object.<string, !WebInspector.TabbedPaneTab>} */
     this._tabsById = {};
     this._currentTabLocked = false;
 
     this._dropDownButton = this._createDropDownButton();
     WebInspector.zoomManager.addEventListener(WebInspector.ZoomManager.Events.ZoomChanged, this._zoomChanged, this);
 }
 
+/** @enum {symbol} */
 WebInspector.TabbedPane.EventTypes = {
-    TabSelected: "TabSelected",
-    TabClosed: "TabClosed",
-    TabOrderChanged: "TabOrderChanged"
+    TabSelected: Symbol("TabSelected"),
+    TabClosed: Symbol("TabClosed"),
+    TabOrderChanged: Symbol("TabOrderChanged")
 }
 
 WebInspector.TabbedPane.prototype = {
     /**
      * @param {boolean} locked
      */
     setCurrentTabLocked: function(locked)
     {
         this._currentTabLocked = locked;
         this._headerElement.classList.toggle("locked", this._currentTabLocked);
@@ skipping 1163 matching lines @@
      * @param {!Array.<string>} ids
      */
     closeTabs: function(tabbedPane, ids) { },
 
     /**
      * @param {string} tabId
      * @param {!WebInspector.ContextMenu} contextMenu
      */
     onContextMenu: function(tabId, contextMenu) { }
 }