Simplify lifecycle notifiers and observers.

Source/core/dom/ContextLifecycleObserver.h

 /*
  * Copyright (C) 2008 Apple 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 13 matching lines @@
  *
  */
 
 #ifndef ContextLifecycleObserver_h
 #define ContextLifecycleObserver_h
 
 #include "core/dom/ExecutionContext.h"
 
 namespace blink {
 
-template<> void observeContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
-template<> void unobserveContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
+class ContextLifecycleNotifier;
 
-class ContextLifecycleObserver : public LifecycleObserver<ExecutionContext> {
+class ContextLifecycleObserver : public LifecycleObserver<ExecutionContext, ContextLifecycleObserver, ContextLifecycleNotifier> {
 public:
+    ExecutionContext* executionContext() const { return lifecycleContext(); }
+
+    enum Type {
+        GenericType,
+        ActiveDOMObjectType,
+    };
+
+    Type observerType() const { return m_observerType; }
+
+protected:
     explicit ContextLifecycleObserver(ExecutionContext*, Type = GenericType);
-    ExecutionContext* executionContext() const { return lifecycleContext(); }
-protected:
+
     virtual ~ContextLifecycleObserver();
+
+private:
+    Type m_observerType;
 };
 
 } // namespace blink
 
 #endif // ContextLifecycleObserver_h