Simplify LifecycleNotifier and Observer.

third_party/WebKit/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
@@ skipping 19 matching lines @@
 #include "core/dom/Document.h"
 #include "platform/LifecycleObserver.h"
 
 namespace blink {
 
 class DocumentLifecycleNotifier;
 
 class CORE_EXPORT DocumentLifecycleObserver : public LifecycleObserver<Document, DocumentLifecycleObserver, DocumentLifecycleNotifier> {
 public:
     virtual void documentWasDetached() { }
-#if !ENABLE(OILPAN)
-    virtual void documentWasDisposed() { }
-#endif
 
 protected:
     explicit DocumentLifecycleObserver(Document* document)
         : LifecycleObserver(document)
     {
     }
 };
 
 } // namespace blink
 
 #endif // DocumentLifecycleObserver_h