Issue 1663 - Emulate background page and implement proper message responder

firstRun.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 238 matching lines @@
   }
 
   function updateToggleButtons()
   {
     ext.backgroundPage.sendMessage({
       type: "subscriptions.get",
       downloadable: true,
       ignoreDisabled: true
     }, function(subscriptions)
     {
+      var known = Object.create(null);
+      for (var i = 0; i < subscriptions.length; i++)
+        known[subscriptions[i].url] = true;
       for (var i = 0; i < featureSubscriptions.length; i++)
       {
         var featureSubscription = featureSubscriptions[i];
-        updateToggleButton(featureSubscription.feature, subscriptions.indexOf(featureSubscription.url) >= 0);
+        updateToggleButton(featureSubscription.feature, featureSubscription.url in known);
       }
     });
   }
 
   function updateToggleButton(feature, isEnabled)
   {
     var button = E("toggle-" + feature);
     if (isEnabled)
       button.classList.remove("off");
     else
       button.classList.add("off");
   }
 
   document.addEventListener("DOMContentLoaded", onDOMLoaded, false);
 })();