diff -r 000000000000 -r 6474c204b198 mobile/android/components/SiteSpecificUserAgent.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/components/SiteSpecificUserAgent.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/UserAgentOverrides.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+const DEFAULT_UA = Cc["@mozilla.org/network/protocol;1?name=http"]
+                     .getService(Ci.nsIHttpProtocolHandler)
+                     .userAgent;
+
+function SiteSpecificUserAgent() {}
+
+SiteSpecificUserAgent.prototype = {
+  getUserAgentForURIAndWindow: function ssua_getUserAgentForURIAndWindow(aURI, aWindow) {
+    let UA;
+    let win = Services.wm.getMostRecentWindow("navigator:browser");
+    if (win && win.DesktopUserAgent) {
+      UA = win.DesktopUserAgent.getUserAgentForWindow(aWindow);
+    }
+    return UA || UserAgentOverrides.getOverrideForURI(aURI) || DEFAULT_UA;
+  },
+
+  classID: Components.ID("{d5234c9d-0ee2-4b3c-9da3-18be9e5cf7e6}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsISiteSpecificUserAgent])
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([SiteSpecificUserAgent]);