Oilpan: Prepare to make ExecutionContext GarbageCollectedMixin.

Source/web/WebSharedWorkerImpl.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 113 matching lines @@
 
     void didReceiveScriptLoaderResponse();
     void onScriptLoaderFinished();
 
     static void connectTask(WebCore::ExecutionContext*, PassOwnPtr<WebMessagePortChannel>);
     // Tasks that are run on the main thread.
     void workerGlobalScopeClosedOnMainThread();
     void workerGlobalScopeDestroyedOnMainThread();
 
     // 'shadow page' - created to proxy loading requests from the worker.
-    RefPtr<WebCore::ExecutionContext> m_loadingDocument;
+    RefPtrWillBePersistent<WebCore::ExecutionContext> m_loadingDocument;
     WebView* m_webView;
     WebFrame* m_mainFrame;
     bool m_askedToTerminate;
 
     RefPtr<WebCore::WorkerThread> m_workerThread;
 
     // This one's initialized and bound to the main thread.
     RefPtr<WeakReference<WebSharedWorkerClient> > m_client;
 
     // Usually WeakPtr is created by WeakPtrFactory exposed by Client
     // class itself, but here it's implemented by Chrome so we create
     // our own WeakPtr.
     WeakPtr<WebSharedWorkerClient> m_clientWeakPtr;
 
     bool m_pauseWorkerContextOnStart;
     bool m_attachDevToolsOnStart;
 
     // Kept around only while main script loading is ongoing.
     OwnPtr<Loader> m_mainScriptLoader;
     WebURL m_url;
     WebString m_name;
     WebString m_contentSecurityPolicy;
     WebContentSecurityPolicyType m_policyType;
 };
 
 } // namespace blink
 
 #endif