compositor-worker: Introduce CompositorWorker.

Source/core/workers/WorkerThread.cpp

Index: Source/core/workers/WorkerThread.cpp
diff --git a/Source/core/workers/WorkerThread.cpp b/Source/core/workers/WorkerThread.cpp
index a389420251d9cb1482a59e70061611d88abedf20..588024cecd00db26e60554b5df979bee0ba938aa 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -290,7 +290,7 @@ void WorkerThread::start()
     if (m_thread)
         return;
 
-    m_thread = WebThreadSupportingGC::create("WebCore: Worker");
+    m_thread = createWebThreadSupportingGC();
     m_thread->postTask(FROM_HERE, new Task(WTF::bind(&WorkerThread::initialize, this)));
 }
 
@@ -359,6 +359,11 @@ void WorkerThread::initialize()
     postDelayedTask(FROM_HERE, createSameThreadTask(&WorkerThread::idleHandler, this), kShortIdleHandlerDelayMs);
 }
 
+PassOwnPtr<WebThreadSupportingGC> WorkerThread::createWebThreadSupportingGC()
+{
+    return WebThreadSupportingGC::create("WebCore: Worker");
+}
+
 void WorkerThread::cleanup()
 {
     // This should be called before we start the shutdown procedure.