Simplify LifecycleNotifier and Observer.

third_party/WebKit/Source/platform/LifecycleObserver.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 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 #ifndef LifecycleObserver_h
 #define LifecycleObserver_h
 
 #include "platform/heap/Handle.h"
-#include "wtf/Assertions.h"
 
 namespace blink {
 
 template<typename T, typename Observer, typename Notifier>
 class LifecycleObserver : public GarbageCollectedMixin {
 public:
     using Context = T;
 
-#if !ENABLE(OILPAN)
-    virtual ~LifecycleObserver()
-    {
-        clearContext();
-    }
-#endif
-
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         visitor->trace(m_lifecycleContext);
     }
 
     virtual void contextDestroyed() { }
 
     Context* lifecycleContext() const { return m_lifecycleContext; }
-    void clearLifecycleContext() { m_lifecycleContext = nullptr; }
 
 protected:
     explicit LifecycleObserver(Context* context)
         : m_lifecycleContext(nullptr)
     {
         setContext(context);
     }
 
     void setContext(Context*);
 
@@ skipping 14 matching lines @@
 
     m_lifecycleContext = context;
 
     if (m_lifecycleContext)
         static_cast<Notifier*>(m_lifecycleContext.get())->addObserver(static_cast<Observer*>(this));
 }
 
 } // namespace blink
 
 #endif // LifecycleObserver_h