diff -r 000000000000 -r 6474c204b198 dom/webidl/CSS.webidl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/webidl/CSS.webidl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,26 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/.
+ *
+ * The origin of this IDL file is
+ * http://dev.w3.org/csswg/css3-conditional/
+ *
+ * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
+ * liability, trademark and document use rules apply.
+ */
+
+[Pref="layout.css.supports-rule.enabled"]
+interface CSS {
+  [Throws, Pref="layout.css.supports-rule.enabled"]
+  static boolean supports(DOMString property, DOMString value);
+
+  [Throws, Pref="layout.css.supports-rule.enabled"]
+  static boolean supports(DOMString conditionText);
+};
+
+// http://dev.w3.org/csswg/cssom/#the-css.escape%28%29-method
+partial interface CSS {
+  [Throws]
+  static DOMString escape(DOMString ident);
+};