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

safari/ext/content.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * 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
@@ skipping 91 matching lines @@
     ))
     {
       event.preventDefault();
 
       // Safari doesn't dispatch an "error" event when preventing an element
       // from loading by cancelling the "beforeload" event. So we have to
       // dispatch it manually. Otherwise element collapsing wouldn't work.
       if (type != "sub_frame")
       {
         var evt = document.createEvent("Event");
-        evt.initEvent(type == "error");
+        evt.initEvent("error");
         event.target.dispatchEvent(evt);
       }
     }
   }, true);
 
 
   /* Context menus */
 
   document.addEventListener("contextmenu", function(event)
   {
@@ skipping 273 matching lines @@
             messageProxy.handleResponse(event.message);
             break;
           case "proxyCallback":
             backgroundPageProxy.handleCallback(event.message);
             break;
         }
       }
     }
   });
 })();