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

third_party/WebKit/Source/devtools/front_end/components/DockController.js

 /*
  * Copyright (C) 2012 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 47 matching lines @@
 
 WebInspector.DockController.State = {
     DockedToBottom: "bottom",
     DockedToRight: "right",
     Undocked: "undocked"
 }
 
 // Use BeforeDockSideChanged to do something before all the UI bits are updated,
 // DockSideChanged to update UI, and AfterDockSideChanged to perform actions
 // after frontend is docked/undocked in the browser.
+
+/** @enum {symbol} */
 WebInspector.DockController.Events = {
-    BeforeDockSideChanged: "BeforeDockSideChanged",
-    DockSideChanged: "DockSideChanged",
-    AfterDockSideChanged: "AfterDockSideChanged"
+    BeforeDockSideChanged: Symbol("BeforeDockSideChanged"),
+    DockSideChanged: Symbol("DockSideChanged"),
+    AfterDockSideChanged: Symbol("AfterDockSideChanged")
 }
 
 WebInspector.DockController.prototype = {
     initialize: function()
     {
         if (!this._canDock)
             return;
 
         this._titles = [WebInspector.UIString("Dock to right"), WebInspector.UIString("Dock to bottom"), WebInspector.UIString("Undock into separate window")];
         this._dockSideChanged();
@@ skipping 141 matching lines @@
     item: function()
     {
         return WebInspector.dockController._closeButton;
     }
 }
 
 /**
  * @type {!WebInspector.DockController}
  */
 WebInspector.dockController;