ServiceWorker: Implement attributes of ExtendableMessageEvent

third_party/WebKit/Source/modules/serviceworkers/ExtendableMessageEventInit.idl

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#extendablemessage-event-section
 
 [
     RuntimeEnabled=ServiceWorkerExtendableMessageEvent,
 ] dictionary ExtendableMessageEventInit : ExtendableEventInit {
-    // TODO(nhiroki): Implement these attributes (crbug.com/543198).
-    // any data;
-    // DOMString origin;
-    // DOMString lastEventId;
-    // (Client or ServiceWorker or MessagePort)? source;
-    // sequence<MessagePort>? ports;
+     any data;
+     DOMString origin;
+     DOMString lastEventId;
+     (Client or ServiceWorker or MessagePort)? source;
+     sequence<MessagePort>? ports;
 };