workers: Move ownership of WebThread from WorkerThread

Source/core/workers/SharedWorkerThread.cpp

 /*
  * Copyright (C) 2009 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 25 matching lines @@
 #include "core/workers/WorkerThreadStartupData.h"
 
 namespace blink {
 
 PassRefPtr<SharedWorkerThread> SharedWorkerThread::create(const String& name, PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerReportingProxy& workerReportingProxy, PassOwnPtr<WorkerThreadStartupData> startupData)
 {
     return adoptRef(new SharedWorkerThread(name, workerLoaderProxy, workerReportingProxy, startupData));
 }
 
 SharedWorkerThread::SharedWorkerThread(const String& name, PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerReportingProxy& workerReportingProxy, PassOwnPtr<WorkerThreadStartupData> startupData)
-    : WorkerThread("SharedWorker Thread", workerLoaderProxy, workerReportingProxy, startupData)
+    : WorkerThread(workerLoaderProxy, workerReportingProxy, startupData)
     , m_name(name.isolatedCopy())
 {
 }
 
 SharedWorkerThread::~SharedWorkerThread()
 {
 }
 
 PassRefPtrWillBeRawPtr<WorkerGlobalScope> SharedWorkerThread::createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData> startupData)
 {
     return SharedWorkerGlobalScope::create(m_name, this, startupData);
 }
 
+WebThreadSupportingGC& SharedWorkerThread::backingThread()
+{
+    if (!m_thread)
+        m_thread = WebThreadSupportingGC::create("SharedWorker Thread");
+    return *m_thread.get();
+}
+
 } // namespace blink