Remove LifecycleNotifier<>::m_context.

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
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  */
 #ifndef LifecycleNotifier_h
 #define LifecycleNotifier_h
 
-#include "platform/LifecycleObserver.h"
+#include "platform/heap/Handle.h"
 #include "wtf/HashSet.h"
-#include "wtf/PassOwnPtr.h"
 #include "wtf/TemporaryChange.h"
 
 namespace blink {
 
 template<typename T, typename Observer>
 class LifecycleNotifier {
 public:
-    typedef T Context;
-
     virtual ~LifecycleNotifier();
-    virtual bool isContextThread() const { return true; }
 
     void addObserver(Observer*);
     void removeObserver(Observer*);
 
     // notifyContextDestroyed() should be explicitly dispatched from an
     // observed context to notify observers that contextDestroyed().
     //
-    // When contextDestroyed() is called, m_context is still
-    // valid and safe to use m_context during the notification.
+    // When contextDestroyed() is called, the observer's lifecycleContext()
+    // is still valid and safe to use during the notification.
     virtual void notifyContextDestroyed();
 
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 
     bool isIteratingOverObservers() const { return m_iterating != IteratingNone; }
 
 protected:
-    explicit LifecycleNotifier(Context* context)
+    LifecycleNotifier()
         : m_iterating(IteratingNone)
-        , m_context(context)
         , m_didCallContextDestroyed(false)
     {
     }
 
-    Context* context() const { return m_context; }
-
     enum IterationType {
         IteratingNone,
         IteratingOverAll,
         IteratingOverActiveDOMObjects,
     };
 
     IterationType m_iterating;
 
 protected:
     using ObserverSet = HashSet<Observer*>;
 
     ObserverSet m_observers;
 
+#if ENABLE(ASSERT)
+    T* context() { return static_cast<T*>(this); }
+#endif
+
 private:
-    Context* m_context;
     bool m_didCallContextDestroyed;
 };
 
 template<typename T, typename Observer>
 inline LifecycleNotifier<T, Observer>::~LifecycleNotifier()
 {
     // FIXME: Enable the following ASSERT. Also see a FIXME in Document::detach().
     // ASSERT(!m_observers.size() || m_didCallContextDestroyed);
 
 #if !ENABLE(OILPAN)
     TemporaryChange<IterationType> scope(m_iterating, IteratingOverAll);
     for (Observer* observer : m_observers) {
-        ASSERT(observer->lifecycleContext() == m_context);
+        ASSERT(observer->lifecycleContext() == context());
         observer->clearLifecycleContext();
     }
 #endif
 }
 
 template<typename T, typename Observer>
 inline void LifecycleNotifier<T, Observer>::notifyContextDestroyed()
 {
     // Don't notify contextDestroyed() twice.
     if (m_didCallContextDestroyed)
         return;
 
     TemporaryChange<IterationType> scope(m_iterating, IteratingOverAll);
     Vector<Observer*> snapshotOfObservers;
     copyToVector(m_observers, snapshotOfObservers);
     for (Observer* observer : snapshotOfObservers) {
         // FIXME: Oilpan: At the moment, it's possible that the Observer is
         // destructed during the iteration. Once we enable Oilpan by default
         // for Observers, we can remove the hack by making m_observers
         // a HeapHashSet<WeakMember<Observers>>. (i.e., we can just iterate
         // m_observers without taking a snapshot).
         if (m_observers.contains(observer)) {
-            ASSERT(observer->lifecycleContext() == m_context);
+            ASSERT(observer->lifecycleContext() == context());
             observer->contextDestroyed();
         }
     }
     m_didCallContextDestroyed = true;
 }
 
 template<typename T, typename Observer>
 inline void LifecycleNotifier<T, Observer>::addObserver(Observer* observer)
 {
     RELEASE_ASSERT(m_iterating != IteratingOverAll);
     m_observers.add(observer);
 }
 
 template<typename T, typename Observer>
 inline void LifecycleNotifier<T, Observer>::removeObserver(Observer* observer)
 {
     m_observers.remove(observer);
 }
 
 } // namespace blink
 
 #endif // LifecycleNotifier_h