Oilpan: keep StashedPortCollection always on the heap.

Source/modules/serviceworkers/StashedPortCollection.h

 // Copyright 2015 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 StashedPortCollection_h
 #define StashedPortCollection_h
 
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/events/EventTarget.h"
 #include "modules/ModulesExport.h"
 #include "modules/serviceworkers/StashedMessagePort.h"
-#include "wtf/RefCounted.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Forward.h"
 
 namespace blink {
 class ScriptState;
-class ScriptValue;
-class ServiceWorkerGlobalScope;
 
 class MODULES_EXPORT StashedPortCollection final
-    : public EventTargetWithInlineData
-    , public RefCountedWillBeNoBase<StashedPortCollection>
+    : public RefCountedGarbageCollectedEventTargetWithInlineData<StashedPortCollection>
     , public ContextLifecycleObserver {
     DEFINE_WRAPPERTYPEINFO();
-    REFCOUNTED_EVENT_TARGET(StashedPortCollection);
+    REFCOUNTED_GARBAGE_COLLECTED_EVENT_TARGET(StashedPortCollection);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(StashedPortCollection);
     WTF_MAKE_NONCOPYABLE(StashedPortCollection);
 public:
-    static PassRefPtrWillBeRawPtr<StashedPortCollection> create(ExecutionContext*);
+    static StashedPortCollection* create(ExecutionContext*);
     virtual ~StashedPortCollection();
 
     void addPorts(const StashedMessagePortArray&);
 
     // StashedPortCollection.idl
     PassRefPtrWillBeRawPtr<StashedMessagePort> add(ScriptState*, const String& name, MessagePort*);
 
     // EventTarget overrides.
     const AtomicString& interfaceName() const override;
     ExecutionContext* executionContext() const override;
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(message);
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit StashedPortCollection(ExecutionContext*);
 
     StashedMessagePortArray m_ports;
 };
 
 } // namespace blink
 
 #endif // StashedPortCollection_h