diff -r 000000000000 -r 6474c204b198 dom/webidl/MessageEvent.webidl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/webidl/MessageEvent.webidl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,53 @@
+/* -*- 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/.
+ *
+ * For more information on this interface, please see
+ * http://www.whatwg.org/specs/web-apps/current-work/#messageevent
+ */
+
+interface WindowProxy;
+
+[Constructor(DOMString type, optional MessageEventInit eventInitDict)]
+interface MessageEvent : Event {
+  /**
+   * Custom data associated with this event.
+   */
+  [GetterThrows]
+  readonly attribute any data;
+
+  /**
+   * The origin of the site from which this event originated, which is the
+   * scheme, ":", and if the URI has a host, "//" followed by the
+   * host, and if the port is not the default for the given scheme,
+   * ":" followed by that port.  This value does not have a trailing slash.
+   */
+  readonly attribute DOMString origin;
+
+  /**
+   * The last event ID string of the event source, for server-sent DOM events; this
+   * value is the empty string for cross-origin messaging.
+   */
+  readonly attribute DOMString lastEventId;
+
+  /**
+   * The window or the port which originated this event.
+   */
+  readonly attribute (WindowProxy or MessagePort)? source;
+
+  /**
+   * Initializes this event with the given data, in a manner analogous to
+   * the similarly-named method on the nsIDOMEvent interface, also setting the
+   * data, origin, source, and lastEventId attributes of this appropriately.
+   */
+  readonly attribute MessagePortList? ports;
+};
+
+dictionary MessageEventInit : EventInit {
+  any data;
+  DOMString origin;
+  DOMString lastEventId;
+  (WindowProxy or MessagePort)? source = null;
+  sequence<MessagePort>? ports;
+};