workers: Move ownership of WebThread from WorkerThread

Source/modules/compositorworker/CompositorWorkerThread.cpp

Index: Source/modules/compositorworker/CompositorWorkerThread.cpp
diff --git a/Source/modules/compositorworker/CompositorWorkerThread.cpp b/Source/modules/compositorworker/CompositorWorkerThread.cpp
index 7cdfff502319b33b52c384ab3c4c09777a5786d2..32ceb1dbe3f3ff435c050709e29d4e2a0375fb57 100644
--- a/Source/modules/compositorworker/CompositorWorkerThread.cpp
+++ b/Source/modules/compositorworker/CompositorWorkerThread.cpp
@@ -20,7 +20,7 @@ PassRefPtr<CompositorWorkerThread> CompositorWorkerThread::create(PassRefPtr<Wor
 }
 
 CompositorWorkerThread::CompositorWorkerThread(PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerObjectProxy& workerObjectProxy, double timeOrigin, PassOwnPtr<WorkerThreadStartupData> startupData)
-    : WorkerThread("CompositorWorker Thread", workerLoaderProxy, workerObjectProxy, startupData)
+    : WorkerThread(workerLoaderProxy, workerObjectProxy, startupData)
     , m_workerObjectProxy(workerObjectProxy)
     , m_timeOrigin(timeOrigin)
 {
@@ -35,4 +35,11 @@ PassRefPtrWillBeRawPtr<WorkerGlobalScope> CompositorWorkerThread::createWorkerGl
     return CompositorWorkerGlobalScope::create(this, startupData, m_timeOrigin);
 }
 
+WebThreadSupportingGC& CompositorWorkerThread::backingThread()
+{
+    if (!m_thread)
+        m_thread = WebThreadSupportingGC::create("CompositorWorker Thread");
+    return *m_thread.get();
+}
+
 } // namespace blink