Oilpan: move WorkerGlobalScope to oilpan's heap.

Source/core/workers/WorkerThread.h

Index: Source/core/workers/WorkerThread.h
diff --git a/Source/core/workers/WorkerThread.h b/Source/core/workers/WorkerThread.h
index a58d1e7210f8386f38f266b3ee47b6a08cdb1191..d280e6edc652ac9881fc2787258af38a86f93d8a 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -77,7 +77,7 @@ namespace WebCore {
         WorkerThread(WorkerLoaderProxy&, WorkerReportingProxy&, PassOwnPtr<WorkerThreadStartupData>);
 
         // Factory method for creating a new worker context for the thread.
-        virtual PassRefPtr<WorkerGlobalScope> createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData>) = 0;
+        virtual PassRefPtrWillBeRawPtr<WorkerGlobalScope> createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData>) = 0;
 
         // Executes the event loop for the worker thread. Derived classes can override to perform actions before/after entering the event loop.
         virtual void runEventLoop();
@@ -95,7 +95,7 @@ namespace WebCore {
         WorkerLoaderProxy& m_workerLoaderProxy;
         WorkerReportingProxy& m_workerReportingProxy;
 
-        RefPtr<WorkerGlobalScope> m_workerGlobalScope;
+        RefPtrWillBePersistent<WorkerGlobalScope> m_workerGlobalScope;
         Mutex m_threadCreationMutex;
 
         OwnPtr<WorkerThreadStartupData> m_startupData;