workers: Move ownership of WebThread from WorkerThread

Source/core/workers/DedicatedWorkerThread.cpp

Index: Source/core/workers/DedicatedWorkerThread.cpp
diff --git a/Source/core/workers/DedicatedWorkerThread.cpp b/Source/core/workers/DedicatedWorkerThread.cpp
index 32665e0807f446fbbca629cd1311a87075f1792f..f7702ba06ea0d0afb53b746b13519db30bfd69fc 100644
--- a/Source/core/workers/DedicatedWorkerThread.cpp
+++ b/Source/core/workers/DedicatedWorkerThread.cpp
@@ -44,7 +44,7 @@ PassRefPtr<DedicatedWorkerThread> DedicatedWorkerThread::create(PassRefPtr<Worke
 }
 
 DedicatedWorkerThread::DedicatedWorkerThread(PassRefPtr<WorkerLoaderProxy> workerLoaderProxy, WorkerObjectProxy& workerObjectProxy, double timeOrigin, PassOwnPtr<WorkerThreadStartupData> startupData)
-    : WorkerThread("DedicatedWorker Thread", workerLoaderProxy, workerObjectProxy, startupData)
+    : WorkerThread(workerLoaderProxy, workerObjectProxy, startupData)
     , m_workerObjectProxy(workerObjectProxy)
     , m_timeOrigin(timeOrigin)
 {
@@ -59,6 +59,13 @@ PassRefPtrWillBeRawPtr<WorkerGlobalScope> DedicatedWorkerThread::createWorkerGlo
     return DedicatedWorkerGlobalScope::create(this, startupData, m_timeOrigin);
 }
 
+WebThreadSupportingGC& DedicatedWorkerThread::backingThread()
+{
+    if (!m_thread)
+        m_thread = WebThreadSupportingGC::create("DedicatedWorker Thread");
+    return *m_thread.get();
+}
+
 void DedicatedWorkerThread::postInitialize()
 {
     // Notify the parent object of our current active state before the event