Remove ActiveDOMObject::willStop, and introduce WorkerGlobalScope::TerminationObserver.

Source/core/dom/ContextLifecycleNotifier.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2013 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:
  * 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
@@ skipping 35 matching lines @@
 
     typedef HashSet<ActiveDOMObject*> ActiveDOMObjectSet;
 
     const ActiveDOMObjectSet& activeDOMObjects() const { return m_activeDOMObjects; }
 
     virtual void addObserver(Observer*) OVERRIDE;
     virtual void removeObserver(Observer*) OVERRIDE;
 
     void notifyResumingActiveDOMObjects();
     void notifySuspendingActiveDOMObjects();
-    void notifyWillStopActiveDOMObjects();
     void notifyStoppingActiveDOMObjects();
 
     bool contains(ActiveDOMObject* object) const { return m_activeDOMObjects.contains(object); }
     bool hasPendingActivity() const;
 
 protected:
     explicit ContextLifecycleNotifier(ExecutionContext*);
 
 private:
     ActiveDOMObjectSet m_activeDOMObjects;
 };
 
 inline PassOwnPtr<ContextLifecycleNotifier> ContextLifecycleNotifier::create(ExecutionContext* context)
 {
     return adoptPtr(new ContextLifecycleNotifier(context));
 }
 
 } // namespace WebCore
 
 #endif // ContextLifecycleNotifier_h