Oilpan: keep StashedPortCollection always on the heap.

Source/modules/serviceworkers/ServiceWorkerGlobalScope.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 50 matching lines @@
 
     virtual ~ServiceWorkerGlobalScope();
     virtual bool isServiceWorkerGlobalScope() const override { return true; }
 
     // WorkerGlobalScope
     virtual void didEvaluateWorkerScript() override;
 
     // ServiceWorkerGlobalScope.idl
     ServiceWorkerClients* clients();
     ServiceWorkerRegistration* registration();
-    PassRefPtrWillBeRawPtr<StashedPortCollection> ports();
+    StashedPortCollection* ports();
 
     ScriptPromise fetch(ScriptState*, const RequestInfo&, const Dictionary&, ExceptionState&);
 
     void close(ExceptionState&);
 
     ScriptPromise skipWaiting(ScriptState*);
 
     void setRegistration(WebServiceWorkerRegistration*);
 
     // EventTarget
@@ skipping 15 matching lines @@
     class SkipWaitingCallback;
 
     ServiceWorkerGlobalScope(const KURL&, const String& userAgent, ServiceWorkerThread*, double timeOrigin, const SecurityOrigin*, PassOwnPtrWillBeRawPtr<WorkerClients>);
     void importScripts(const Vector<String>& urls, ExceptionState&) override;
     PassOwnPtr<CachedMetadataHandler> createWorkerScriptCachedMetadataHandler(const KURL& scriptURL, const Vector<char>* metaData) override;
     void logExceptionToConsole(const String& errorMessage, int scriptId, const String& sourceURL, int lineNumber, int columnNumber, PassRefPtrWillBeRawPtr<ScriptCallStack>) override;
     void scriptLoaded(size_t scriptSize, size_t cachedMetadataSize) override;
 
     PersistentWillBeMember<ServiceWorkerClients> m_clients;
     PersistentWillBeMember<ServiceWorkerRegistration> m_registration;
-    RefPtrWillBeMember<StashedPortCollection> m_ports;
+    PersistentWillBeMember<StashedPortCollection> m_ports;
     bool m_didEvaluateScript;
     bool m_hadErrorInTopLevelEventHandler;
     unsigned m_eventNestingLevel;
     size_t m_scriptCount;
     size_t m_scriptTotalSize;
     size_t m_scriptCachedMetadataTotalSize;
 };
 
 DEFINE_TYPE_CASTS(ServiceWorkerGlobalScope, ExecutionContext, context, context->isServiceWorkerGlobalScope(), context.isServiceWorkerGlobalScope());
 
 } // namespace blink
 
 #endif // ServiceWorkerGlobalScope_h