Simplify ownership of a ThreadState's interruptors.

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 153 matching lines @@
 
     RefPtrWillBePersistent<WorkerInspectorController> m_workerInspectorController;
     Mutex m_workerInspectorControllerMutex;
 
     // This lock protects |m_workerGlobalScope|, |m_terminated|, |m_isolate| and |m_microtaskRunner|.
     Mutex m_threadStateMutex;
 
     RefPtrWillBePersistent<WorkerGlobalScope> m_workerGlobalScope;
 
     v8::Isolate* m_isolate;
-    OwnPtr<V8IsolateInterruptor> m_interruptor;
 
     // Used to signal thread shutdown.
     OwnPtr<WebWaitableEvent> m_shutdownEvent;
 
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 };
 
 } // namespace blink
 
 #endif // WorkerThread_h