Fix data race in blink::WorkerMessagingProxy::reportException

Source/core/workers/WorkerThread.h

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 88 matching lines @@
     void appendDebuggerTask(PassOwnPtr<WebThread::Task>);
 
     enum WaitMode { WaitForMessage, DontWaitForMessage };
     MessageQueueWaitResult runDebuggerTask(WaitMode = WaitForMessage);
 
     // These methods should be called if the holder of the thread is
     // going to call runDebuggerTask in a loop.
     void willEnterNestedLoop();
     void didLeaveNestedLoop();
 
-    WorkerGlobalScope* workerGlobalScope() const { return m_workerGlobalScope.get(); }
+    // Can be called only on the worker thread, WorkerGlobalScope is not thread safe.
+    WorkerGlobalScope* workerGlobalScope();
 
     // Returns true once one of the terminate* methods is called.
     bool terminated();
 
     // Number of active worker threads.
     static unsigned workerThreadCount();
 
     PlatformThreadId platformThreadId();
 
     void interruptAndDispatchInspectorCommands();
@@ skipping 55 matching lines @@
     // Used to signal thread shutdown.
     OwnPtr<WebWaitableEvent> m_shutdownEvent;
 
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 };
 
 } // namespace blink
 
 #endif // WorkerThread_h