Remove LifecycleNotifier<>::m_context.

Source/core/dom/DocumentLifecycleNotifier.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 21 matching lines @@
 
 class Document;
 class DocumentLifecycleObserver;
 
 class DocumentLifecycleNotifier : public LifecycleNotifier<Document, DocumentLifecycleObserver> {
 public:
     void notifyDocumentWasDetached();
 #if !ENABLE(OILPAN)
     void notifyDocumentWasDisposed();
 #endif
-
-protected:
-    explicit DocumentLifecycleNotifier(Document*);
 };
 
 } // namespace blink
 
 #endif // DocumentLifecycleNotifier_h