Issue 3427 - Ensure consistent behavior of EventTarget if listeners remove themselves when called

ext/common.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 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
@@ skipping 21 matching lines @@
     },
     removeListener: function(listener)
     {
       var idx = this._listeners.indexOf(listener);
       if (idx != -1)
         this._listeners.splice(idx, 1);
     },
     _dispatch: function()
     {
       var results = [];
+      var listeners = this._listeners.slice();
 
-      for (var i = 0; i < this._listeners.length; i++)
-        results.push(this._listeners[i].apply(null, arguments));
+      for (var i = 0; i < listeners.length; i++)
+        results.push(listeners[i].apply(null, arguments));
 
       return results;
     }
   };
 })();