Oilpan: keep StashedPortCollection always on the heap.

Source/modules/serviceworkers/ServiceWorkerGlobalScope.cpp

 /*
  * 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 99 matching lines @@
 {
     if (Platform* platform = Platform::current()) {
         platform->histogramCustomCounts("ServiceWorker.ScriptCount", m_scriptCount, 1, 1000, 50);
         platform->histogramCustomCounts("ServiceWorker.ScriptTotalSize", m_scriptTotalSize, 1000, 5000000, 50);
         if (m_scriptCachedMetadataTotalSize)
             platform->histogramCustomCounts("ServiceWorker.ScriptCachedMetadataTotalSize", m_scriptCachedMetadataTotalSize, 1000, 50000000, 50);
     }
     m_didEvaluateScript = true;
 }
 
-PassRefPtrWillBeRawPtr<StashedPortCollection> ServiceWorkerGlobalScope::ports()
+StashedPortCollection* ServiceWorkerGlobalScope::ports()
 {
     if (!m_ports)
         m_ports = StashedPortCollection::create(this);
     return m_ports;
 }
 
 ScriptPromise ServiceWorkerGlobalScope::fetch(ScriptState* scriptState, const RequestInfo& input, const Dictionary& init, ExceptionState& exceptionState)
 {
     return GlobalFetch::fetch(scriptState, *this, input, init, exceptionState);
 }
@@ skipping 112 matching lines @@
 }
 
 void ServiceWorkerGlobalScope::scriptLoaded(size_t scriptSize, size_t cachedMetadataSize)
 {
     ++m_scriptCount;
     m_scriptTotalSize += scriptSize;
     m_scriptCachedMetadataTotalSize += cachedMetadataSize;
 }
 
 } // namespace blink