Verify that ExtendableMessageEvent's message ports reside on the same heap

third_party/WebKit/Source/modules/serviceworkers/ExtendableMessageEvent.h

 // 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.
 
 #ifndef ExtendableMessageEvent_h
 #define ExtendableMessageEvent_h
 
 #include "modules/EventModules.h"
 #include "modules/ModulesExport.h"
 #include "modules/serviceworkers/ExtendableEvent.h"
@@ skipping 53 matching lines @@
                          const String& origin,
                          MessagePortArray* ports,
                          WaitUntilObserver*);
 
   RefPtr<SerializedScriptValue> m_serializedData;
   String m_origin;
   String m_lastEventId;
   Member<ServiceWorkerClient> m_sourceAsClient;
   Member<ServiceWorker> m_sourceAsServiceWorker;
   Member<MessagePort> m_sourceAsMessagePort;
-  Member<MessagePortArray> m_ports;
+  // TODO(sof): remove once crbug.com/655926 has been addressed.
+  SameThreadCheckedMember<MessagePortArray> m_ports;
 };
 
 }  // namespace blink
 
 #endif  // ExtendableMessageEvent_h