Issue 1528 - Implemented backend for general tab of new options page

ext/background.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 58 matching lines @@
       if (index >= 0)
       {
         this._keys.splice(index, 1);
         this._values.splice(index, 1);
       }
     }
   };
 
   global.ext.PageMap = PageMap;
 
-  global.ext.showOptions = function()
+  global.ext.showOptions = function(callback)
   {
-    window.open("http://example.com/options.html", "_blank");
+    if (top.location.href.indexOf("options.html") == -1)
+      window.open("options.html", "_blank");
+
+    if (callback)
+      callback();
   };
 })(this);