Revert of Revert "Typecheck JS files for chrome://extensions"

ui/webui/resources/js/cr/event_target.js

 // Copyright (c) 2010 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.
 
 /**
  * @fileoverview This contains an implementation of the EventTarget interface
  * as defined by DOM Level 2 Events.
  */
 
 cr.define('cr', function() {
@@ skipping 44 matching lines @@
             delete this.listeners_[type];
           else
             handlers.splice(index, 1);
         }
       }
     },
 
     /**
      * Dispatches an event and calls all the listeners that are listening to
      * the type of the event.
-     * @param {!cr.event.Event} event The event to dispatch.
+     * @param {!Event} event The event to dispatch.
      * @return {boolean} Whether the default action was prevented. If someone
      *     calls preventDefault on the event object then this returns false.
      */
     dispatchEvent: function(event) {
       if (!this.listeners_)
         return true;
 
       // Since we are using DOM Event objects we need to override some of the
       // properties and methods so that we can emulate this correctly.
       var self = this;
@@ skipping 16 matching lines @@
 
       return !prevented && !event.defaultPrevented;
     }
   };
 
   // Export
   return {
     EventTarget: EventTarget
   };
 });