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

Source/core/page/PageLifecycleObserver.cpp

 /*
  * 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
@@ skipping 10 matching lines @@
  * 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.
  */
 
 
 #include "config.h"
 #include "core/page/PageLifecycleObserver.h"
 
 #include "core/page/Page.h"
-#include "core/page/PageLifecycleNotifier.h"
 
 namespace blink {
 
-template<> void observeContext(Page* context, LifecycleObserver<Page>* observer)
+template<> void observerContext(Page* context, LifecycleObserver<Page>* observer)
 {
-    context->addObserver(observer);
+    context->wasObservedBy(observer);
 }
 
-template<> void unobserveContext(Page* context, LifecycleObserver<Page>* observer)
+template<> void unobserverContext(Page* context, LifecycleObserver<Page>* observer)
 {
-    context->removeObserver(observer);
+    context->wasUnobservedBy(observer);
 }
 
 PageLifecycleObserver::PageLifecycleObserver(Page* page)
     : LifecycleObserver<Page>(page, PageLifecycleObserverType)
 {
 }
 
 PageLifecycleObserver::~PageLifecycleObserver()
 {
 }
 
 Page* PageLifecycleObserver::page() const
 {
     return static_cast<Page*>(lifecycleContext());
 }
 
 } // namespace blink