When applying to windows on install, use front-to-back order (seebug 819561)

lib/windowObserver.js

 /*
  * This file is part of the Adblock Plus build tools,
  * Copyright (C) 2006-2012 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 17 matching lines @@
  * @param {String} [when]   when to execute applyToWindow(). "start" means immediately
  *                          when the window opens, "ready" when its contents are available
  *                          and "end" (default) means to wait until the "load" event.
  * @constructor
  */
 function WindowObserver(listener, when)
 {
   this._listener  = listener;
   this._when = when;
 
-  let e = Services.ww.getWindowEnumerator();
+  let e = Services.wm.getZOrderDOMWindowEnumerator(null, true);
+  if (!e.hasMoreElements())
+  {
+    // On Linux the list returned will be empty, see bug 156333. Fall back to random order.
+    e = Services.wm.getEnumerator(null);
+  }
   while (e.hasMoreElements())
   {
     let window = e.getNext().QueryInterface(Ci.nsIDOMWindow);
     if (when == "start" || window.document.readyState == "complete")
       this._listener.applyToWindow(window);
     else
       this.observe(window, "chrome-document-global-created", null);
   }
 
   Services.obs.addObserver(this, "chrome-document-global-created", true);
@@ skipping 41 matching lines @@
         window.removeEventListener(event, listener, false);
         if (this._shutdownHandler)
           this._listener.applyToWindow(window);
       }.bind(this);
       window.addEventListener(event, listener, false);
     }
   },
 
   QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference, Ci.nsIObserver])
 };