Fix: issue with chrome v28 and below

chrome/ext/background.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2013 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 168 matching lines @@
 
   var BackgroundMessageEventTarget = function()
   {
     MessageEventTarget.call(this);
   }
   BackgroundMessageEventTarget.prototype = {
     __proto__: MessageEventTarget.prototype,
     _wrapSender: function(sender)
     {
       var tab = new Tab(sender.tab);
+      if (sender.url == null);

[Thomas Greiner, 2014/02/10 11:05:34]

Add a comment above why this is necessary and investigate further which versions
are affected by this so that we know when it's safe to get rid of it again.

e.g. "Chrome 21-26 does not pass sender.url"

+        sender.url = tab.url;
       return {tab: tab, frame: new Frame({url: sender.url, tab: tab})};
     }
   };
 
 
   /* Tabs */
 
   var sendMessage = chrome.tabs.sendMessage || chrome.tabs.sendRequest;
 
   var BrowserAction = function(tabId)
@@ skipping 374 matching lines @@
       if (isContextMenuHidden)
         return;
 
       chrome.contextMenus.removeAll();
       isContextMenuHidden = true;
     }
   };
 
   ext.onMessage = new BackgroundMessageEventTarget();
 })();