compositor-worker: Introduce CompositorWorker.

Source/core/workers/WorkerMessagingProxy.cpp

Index: Source/core/workers/WorkerMessagingProxy.cpp
diff --git a/Source/core/workers/WorkerMessagingProxy.cpp b/Source/core/workers/WorkerMessagingProxy.cpp
index a1e4abde82d0b099d1efbdcad6a0aac35dcb0884..7f3b201e8bb0b668133b59fe6b92b6b97f1b6ee0 100644
--- a/Source/core/workers/WorkerMessagingProxy.cpp
+++ b/Source/core/workers/WorkerMessagingProxy.cpp
@@ -125,7 +125,7 @@ void WorkerMessagingProxy::startWorkerGlobalScope(const KURL& scriptURL, const S
     double originTime = document->loader() ? document->loader()->timing().referenceMonotonicTime() : monotonicallyIncreasingTime();
 
     m_loaderProxy = WorkerLoaderProxy::create(this);
-    RefPtr<DedicatedWorkerThread> thread = DedicatedWorkerThread::create(m_loaderProxy, *m_workerObjectProxy.get(), originTime, startupData.release());
+    RefPtr<DedicatedWorkerThread> thread = createWorkerThread(originTime, startupData.release());
     thread->start();
     workerThreadCreated(thread);
     m_workerInspectorProxy->workerThreadCreated(m_executionContext.get(), m_workerThread.get(), scriptURL);
@@ -213,6 +213,11 @@ void WorkerMessagingProxy::workerThreadCreated(PassRefPtr<DedicatedWorkerThread>
     m_queuedEarlyTasks.clear();
 }
 
+PassRefPtr<DedicatedWorkerThread> WorkerMessagingProxy::createWorkerThread(double originTime, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData> startupData)
+{
+    return DedicatedWorkerThread::create(loaderProxy(), workerObjectProxy(), originTime, startupData);
+}
+
 void WorkerMessagingProxy::workerObjectDestroyed()
 {
     m_workerObject = nullptr;