Remove LifecycleNotifier<>::m_context.

Source/core/page/PageLifecycleNotifier.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
@@ skipping 20 matching lines @@
 namespace blink {
 
 class LocalFrame;
 class Page;
 class PageLifecycleObserver;
 
 class PageLifecycleNotifier : public LifecycleNotifier<Page, PageLifecycleObserver> {
 public:
     void notifyPageVisibilityChanged();
     void notifyDidCommitLoad(LocalFrame*);
-
-protected:
-    explicit PageLifecycleNotifier(Page*);
 };
 
 } // namespace blink
 
 #endif // PageLifecycleNotifier_h