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

Source/core/page/PageLifecycleNotifier.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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 PageLifecycleNotifier_h
 #define PageLifecycleNotifier_h
 
+#include "core/page/Page.h"
+#include "core/page/PageLifecycleObserver.h"
 #include "platform/LifecycleNotifier.h"
-#include "wtf/HashSet.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/TemporaryChange.h"
 
 namespace blink {
 
 class LocalFrame;
-class Page;
-class PageLifecycleObserver;
 
-class PageLifecycleNotifier : public LifecycleNotifier<Page> {
+class PageLifecycleNotifier final : public LifecycleNotifier<Page> {
 public:
+    static PassOwnPtr<PageLifecycleNotifier> create(Page*);
+
     void notifyPageVisibilityChanged();
     void notifyDidCommitLoad(LocalFrame*);
 
     virtual void addObserver(Observer*) override;
     virtual void removeObserver(Observer*) override;
 
-protected:
+private:
     explicit PageLifecycleNotifier(Page*);
 
-private:
     using PageObserverSet = HashSet<PageLifecycleObserver*>;
     PageObserverSet m_pageObservers;
 };
 
+inline PassOwnPtr<PageLifecycleNotifier> PageLifecycleNotifier::create(Page* context)
+{
+    return adoptPtr(new PageLifecycleNotifier(context));
+}
+
+inline void PageLifecycleNotifier::notifyPageVisibilityChanged()
+{
+    TemporaryChange<IterationType> scope(this->m_iterating, IteratingOverPageObservers);
+    for (PageLifecycleObserver* pageObserver : m_pageObservers)
+        pageObserver->pageVisibilityChanged();
+}
+
+inline void PageLifecycleNotifier::notifyDidCommitLoad(LocalFrame* frame)
+{
+    TemporaryChange<IterationType> scope(this->m_iterating, IteratingOverPageObservers);
+    for (PageLifecycleObserver* pageObserver : m_pageObservers)
+        pageObserver->didCommitLoad(frame);
+}
+
 } // namespace blink
 
 #endif // PageLifecycleNotifier_h