Issue 3348 - Element Hiding Helper UI broken after bug 1182546 landing

lib/main.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 let {Services} = Cu.import("resource://gre/modules/Services.jsm", {});
 
 let {Prefs} = require("prefs");
 let {WindowObserver} = require("windowObserver");
@@ skipping 41 matching lines @@
   .getService(Ci.nsIFrameScriptLoader);
 messageManager.loadFrameScript(frameScript, true);
 onShutdown.add(() => {
   messageManager.removeDelayedFrameScript(frameScript);
   messageManager.QueryInterface(Ci.nsIMessageBroadcaster).broadcastAsyncMessage("ElemHideHelper:Shutdown");
 });
 
 // Load overlay asynchonously and start attaching to windows once done
 request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIJSXMLHttpRequest);
 request.open("GET", "chrome://elemhidehelper/content/overlay.xul");
+request.channel.owner = Cc["@mozilla.org/systemprincipal;1"].getService(Ci.nsIPrincipal);
 request.addEventListener("load", function(event)
 {
   if (onShutdown.done)
     return;
 
   let overlay = event.target.responseXML.documentElement;
 
   // Initialization done, we can start up now
   require("inspectorObserver");
   new WindowObserver({
@@ skipping 23 matching lines @@
       if (element)
         element.parentNode.removeChild(element);
 
       for (let child = window.document.firstChild; child; child = child.nextSibling)
         if (child.nodeType == child.PROCESSING_INSTRUCTION_NODE && child.data.indexOf("elemhidehelper-node") >= 0)
           child.parentNode.removeChild(child);
     }
   });
 }, false);
 request.send(null);