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

Source/modules/compositorworker/CompositorWorkerManager.cpp

Index: Source/modules/compositorworker/CompositorWorkerManager.cpp
diff --git a/Source/modules/compositorworker/CompositorWorkerManager.cpp b/Source/modules/compositorworker/CompositorWorkerManager.cpp
index 62dc23b4c02a2ce82f05a4a82fc2cac2460c447f..70430cbc33d269c9836cfb3ef1991bf8b2b5bf8c 100644
--- a/Source/modules/compositorworker/CompositorWorkerManager.cpp
+++ b/Source/modules/compositorworker/CompositorWorkerManager.cpp
@@ -26,7 +26,7 @@ static Mutex& singletonMutex()
     return mutex;
 }
 
-static void destroyThread(WebThreadSupportingGC* thread)
+static void destroyThread(WebThread* thread)
 {
     delete thread;
 }
@@ -63,15 +63,17 @@ CompositorWorkerManager::~CompositorWorkerManager()
 {
 }
 
-WebThreadSupportingGC& CompositorWorkerManager::compositorWorkerThread()
+WebThread& CompositorWorkerManager::compositorWorkerThread()
 {
     MutexLocker lock(m_mutex);
     if (!m_thread) {
         ASSERT(isMainThread());
         ASSERT(!m_workerCount);
-        m_thread = WebThreadSupportingGC::create("CompositorWorker Thread");
+        // TODO(sad): Instead of creating a new thread, retrieve the thread from Platform using a more
+        // specialized function (e.g. Platform::comositorWorkerThread()).
+        m_thread = adoptPtr(Platform::current()->createThread("CompositorWorker Thread"));
     }
-    return *m_thread.get();
+    return *m_thread;
 }
 
 void CompositorWorkerManager::initializeBackingThread()
@@ -82,7 +84,8 @@ void CompositorWorkerManager::initializeBackingThread()
     if (m_workerCount > 1)
         return;
 
-    m_thread->initialize();
+    ASSERT(!m_gcSupport);
+    m_gcSupport = GCSupportForWebThread::create(*m_thread);
 
     // Initialize the isolate at the same time.
     ASSERT(!m_isolate);
@@ -101,7 +104,7 @@ void CompositorWorkerManager::shutdownBackingThread()
     ASSERT(m_workerCount > 0);
     --m_workerCount;
     if (m_workerCount == 0) {
-        m_thread->shutdown();
+        m_gcSupport.clear();
         Platform::current()->mainThread()->postTask(FROM_HERE, threadSafeBind(destroyThread, AllowCrossThreadAccess(m_thread.leakPtr())));
         m_thread = nullptr;
     }