compositor-worker: Get the thread to run compositor-workers from the Platform.

Source/modules/compositorworker/CompositorWorkerThread.cpp

 // 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.
 
 #include "config.h"
 #include "modules/compositorworker/CompositorWorkerThread.h"
 
 #include "bindings/core/v8/V8Initializer.h"
 #include "core/workers/WorkerObjectProxy.h"
 #include "core/workers/WorkerThreadStartupData.h"
@@ skipping 18 matching lines @@
 
 CompositorWorkerThread::~CompositorWorkerThread()
 {
 }
 
 PassRefPtrWillBeRawPtr<WorkerGlobalScope> CompositorWorkerThread::createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData> startupData)
 {
     return CompositorWorkerGlobalScope::create(this, startupData, m_timeOrigin);
 }
 
-WebThreadSupportingGC& CompositorWorkerThread::backingThread()
+WebThread& CompositorWorkerThread::backingThread()
 {
     return CompositorWorkerManager::instance()->compositorWorkerThread();
 }
 
 void CompositorWorkerThread::initializeBackingThread()
 {
     CompositorWorkerManager::instance()->initializeBackingThread();
 }
 
 void CompositorWorkerThread::shutdownBackingThread()
@@ skipping 15 matching lines @@
 {
     CompositorWorkerManager::instance()->destroyIsolate();
 }
 
 void CompositorWorkerThread::terminateV8Execution()
 {
     CompositorWorkerManager::instance()->terminateV8Execution();
 }
 
 } // namespace blink