diff -r 000000000000 -r 6474c204b198 toolkit/content/menulist.css
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/content/menulist.css	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,11 @@
+/* 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/. */
+
+@namespace html url("http://www.w3.org/1999/xhtml"); /* namespace for HTML elements */
+
+html|*.menulist-editable-input {
+  -moz-appearance: none !important;
+  background: transparent ! important;
+  -moz-box-flex: 1;
+}