diff -r 000000000000 -r 6474c204b198 toolkit/content/select-child.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/content/select-child.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,13 @@
+/* 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/. */
+
+XPCOMUtils.defineLazyModuleGetter(this, "SelectContentHelper",
+                                  "resource://gre/modules/SelectContentHelper.jsm");
+
+addEventListener("mozshowdropdown", event => {
+  if (!event.isTrusted)
+    return;
+
+  new SelectContentHelper(event.target, this);
+});