diff -r 000000000000 -r 6474c204b198 dom/webidl/MozTimeManager.webidl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/webidl/MozTimeManager.webidl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,18 @@
+/* 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/. */
+
+[Func="mozilla::dom::time::TimeManager::PrefEnabled"]
+interface MozTimeManager {
+  /* Set the system time.
+   *
+   * The |time| argument can be either a Date object or a number.
+   *
+   * - If |time| is a number, it's interpreted as milliseconds
+   *   since the epoch (midnight UTC on January 1, 1970).
+   * - If |time| is a Date object, |set(time)| is equivalent to
+   *   |set(time.getTime())|.
+   */
+  void set(Date time);
+  void set(double time);
+};