Simplify lifecycle notifiers and observers.

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 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef DocumentLifecycleObserver_h
 #define DocumentLifecycleObserver_h
 
 #include "core/dom/Document.h"
 
 namespace blink {
 
-template<> void observeContext(Document*, LifecycleObserver<Document>*);
-template<> void unobserveContext(Document*, LifecycleObserver<Document>*);
+class DocumentLifecycleNotifier;
 
-class DocumentLifecycleObserver : public LifecycleObserver<Document> {
+class DocumentLifecycleObserver : public LifecycleObserver<Document, DocumentLifecycleObserver, DocumentLifecycleNotifier> {
 public:
-    explicit DocumentLifecycleObserver(Document*);
-    virtual ~DocumentLifecycleObserver();
     virtual void documentWasDetached() { }
 #if !ENABLE(OILPAN)
     virtual void documentWasDisposed() { }
 #endif
+
+protected:
+    explicit DocumentLifecycleObserver(Document*);
+    virtual ~DocumentLifecycleObserver();
 };
 
 } // namespace blink
 
 #endif // DocumentLifecycleObserver_h