Use XMLHttpRequest constructor in JS modules

lib/io.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 54 matching lines @@
    * Reads strings from a file asynchronously, calls listener.process() with
    * each line read and with a null parameter once the read operation is done.
    * The callback will be called when the operation is done.
    */
   readFromFile: function(/**nsIFile|nsIURI*/ file, /**Boolean*/ decode, /**Object*/ listener, /**Function*/ callback, /**String*/ timeLineID)
   {
     try
     {
       let buffer = "";
       let uri = file instanceof Ci.nsIFile ? Services.io.newFileURI(file) : file;
-      let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);
+      let request = new XMLHttpRequest();
       request.mozBackgroundRequest = true;
       request.open("GET", uri.spec);
       request.responseType = "moz-chunked-text";
       request.overrideMimeType("text/plain" + (decode ? "? charset=utf-8" : ""));
 
       request.addEventListener("progress", function(event)
       {
         if (timeLineID)
         {
           TimeLine.asyncStart(timeLineID);
@@ skipping 244 matching lines @@
         isFile: exists && file.isFile(),
         lastModified: exists ? file.lastModifiedTime : 0
       });
     }
     catch(e)
     {
       callback(e);
     }
   }
 }