Revert r189385 "Remove LifecycleContext" and r189391, r189530, r189456 that block it

Source/core/dom/ContextLifecycleNotifier.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
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
-
 #ifndef ContextLifecycleNotifier_h
 #define ContextLifecycleNotifier_h
 
+#include "core/dom/ExecutionContext.h"
 #include "platform/LifecycleNotifier.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class ActiveDOMObject;
-class ExecutionContext;
 
 class ContextLifecycleNotifier : public LifecycleNotifier<ExecutionContext> {
 public:
+    static PassOwnPtr<ContextLifecycleNotifier> create(ExecutionContext*);
+
+    virtual ~ContextLifecycleNotifier();
+
     typedef HashSet<ActiveDOMObject*> ActiveDOMObjectSet;
 
     const ActiveDOMObjectSet& activeDOMObjects() const { return m_activeDOMObjects; }
 
     virtual void addObserver(Observer*) override;
     virtual void removeObserver(Observer*) override;
 
     void notifyResumingActiveDOMObjects();
     void notifySuspendingActiveDOMObjects();
     void notifyStoppingActiveDOMObjects();
 
     bool contains(ActiveDOMObject* object) const { return m_activeDOMObjects.contains(object); }
     bool hasPendingActivity() const;
 
 protected:
     explicit ContextLifecycleNotifier(ExecutionContext*);
 
 private:
     ActiveDOMObjectSet m_activeDOMObjects;
 };
 
+inline PassOwnPtr<ContextLifecycleNotifier> ContextLifecycleNotifier::create(ExecutionContext* context)
+{
+    return adoptPtr(new ContextLifecycleNotifier(context));
+}
+
 } // namespace blink
 
 #endif // ContextLifecycleNotifier_h