Refactored the abstraction layer to address prerendered pages on Safari caused by leaky abstraction

ext/common.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
- * Copyright (C) 2006-2013 Eyeo GmbH
+ * Copyright (C) 2006-2014 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 
 (function()
 {
   window.ext = {};
 
   var EventTarget = ext._EventTarget = function(cancelable)
   {
     this._listeners = [];
     this._cancelable = cancelable;
   };
   EventTarget.prototype = {
     addListener: function(listener)
     {
-      this._listeners.push(listener);

[Wladimir Palant, 2014/04/04 14:00:35]

Please check first whether this listener is already in the list, just in case.

[Sebastian Noack, 2014/04/07 13:15:25]

Done.

+      if (this._listeners.indexOf(listener) == -1)
+        this._listeners.push(listener);
     },
     removeListener: function(listener)
     {
       var idx = this._listeners.indexOf(listener);
       if (idx != -1)
         this._listeners.splice(idx, 1);
     },
     _dispatch: function(cancelable, args)
     {
       for (var i = 0; i < this._listeners.length; i++)
       {
         var result = this._listeners[i].apply(null, arguments);
         if (this._cancelable && result === false)
           return false;
       }
       return true;
     }
   };
 })();