Remove LifecycleNotifier<>::m_context.

Source/core/dom/DocumentLifecycleObserver.h

 /*
  * 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
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * 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 DocumentLifecycleObserver_h
 #define DocumentLifecycleObserver_h
 
 #include "core/dom/Document.h"
+#include "platform/LifecycleObserver.h"
 
 namespace blink {
 
 class DocumentLifecycleNotifier;
 
 class DocumentLifecycleObserver : public LifecycleObserver<Document, DocumentLifecycleObserver, DocumentLifecycleNotifier> {
 public:
     virtual void documentWasDetached() { }
 #if !ENABLE(OILPAN)
     virtual void documentWasDisposed() { }
 #endif
 
 protected:
     explicit DocumentLifecycleObserver(Document*);
     virtual ~DocumentLifecycleObserver();
 };
 
 } // namespace blink
 
 #endif // DocumentLifecycleObserver_h