Use XMLHttpRequest constructor in JS modules

lib/ui.js

Index: lib/ui.js
===================================================================
--- a/lib/ui.js
+++ b/lib/ui.js
@@ -155,17 +155,17 @@ let optionsObserver =
         addCommandHandler("adblockplus-showinaddonbar", handler);
         addCommandHandler("adblockplus-showintoolbar", handler);
       }
 
       let list = doc.getElementById("adblockplus-subscription-list");
       if (list)
       {
         // Load subscriptions data
-        let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);
+        let request = new XMLHttpRequest();
         request.mozBackgroundRequest = true;
         request.open("GET", "chrome://adblockplus/content/ui/subscriptions.xml");
         request.addEventListener("load", function()
         {
           if (onShutdown.done)
             return;
 
           let currentSubscription = FilterStorage.subscriptions.filter(
@@ -279,17 +279,17 @@ let UI = exports.UI =
   init: function()
   {
     // We should call initDone once both overlay and filters are loaded
     let overlayLoaded = false;
     let filtersLoaded = false;
     let sessionRestored = false;
 
     // Start loading overlay
-    let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIJSXMLHttpRequest);
+    let request = new XMLHttpRequest();
     request.mozBackgroundRequest = true;
     request.open("GET", "chrome://adblockplus/content/ui/overlay.xul");
     request.addEventListener("load", function(event)
     {
       if (onShutdown.done)
         return;
 
       this.processOverlay(request.responseXML.documentElement);
@@ -789,17 +789,17 @@ let UI = exports.UI =
                                "data:application/vnd.mozilla.xul+xml," + encodeURIComponent(dialogSource),
                                "_blank", "chrome,centerscreen,resizable,dialog=no", null);
       }
     }
 
     if (addSubscription)
     {
       // Load subscriptions data
-      let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);
+      let request = new XMLHttpRequest();
       request.mozBackgroundRequest = true;
       request.open("GET", "chrome://adblockplus/content/ui/subscriptions.xml");
       request.addEventListener("load", function()
       {
         if (onShutdown.done)
           return;
 
         let node = Utils.chooseFilterSubscription(request.responseXML.getElementsByTagName("subscription"));