Clean up forward declarations in Source/platform

Source/platform/LifecycleNotifier.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * 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
@@ skipping 16 matching lines @@
 #ifndef LifecycleNotifier_h
 #define LifecycleNotifier_h
 
 #include "platform/LifecycleObserver.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/TemporaryChange.h"
 
 namespace blink {
 
-template<typename T> class LifecycleContext;
-
 template<typename T>
 class LifecycleNotifier {
 public:
     typedef LifecycleObserver<T> Observer;
     typedef T Context;
 
     static PassOwnPtr<LifecycleNotifier> create(Context* context)
     {
         return adoptPtr(new LifecycleNotifier(context));
     }
@@ skipping 60 matching lines @@
 {
     RELEASE_ASSERT(m_iterating != IteratingOverAll);
     m_observers.remove(observer);
 }
 
 
 
 } // namespace blink
 
 #endif // LifecycleNotifier_h