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

Source/core/dom/DocumentLifecycleObserver.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/dom/DocumentLifecycleObserver.h"
 
 #include "core/dom/Document.h"
-#include "core/dom/DocumentLifecycleNotifier.h"
 
 namespace blink {
 
-template<> void observeContext(Document* context, LifecycleObserver<Document>* observer)
+template<> void observerContext(Document* context, LifecycleObserver<Document>* observer)
 {
-    static_cast<DocumentLifecycleNotifier*>(context)->addObserver(observer);
+    static_cast<LifecycleContext<Document>*>(context)->wasObservedBy(observer);
 }
 
-template<> void unobserveContext(Document* context, LifecycleObserver<Document>* observer)
+template<> void unobserverContext(Document* context, LifecycleObserver<Document>* observer)
 {
-    static_cast<DocumentLifecycleNotifier*>(context)->removeObserver(observer);
+    static_cast<LifecycleContext<Document>*>(context)->wasUnobservedBy(observer);
 }
 
 DocumentLifecycleObserver::DocumentLifecycleObserver(Document* document)
     : LifecycleObserver<Document>(document, DocumentLifecycleObserverType)
 {
 }
 
 DocumentLifecycleObserver::~DocumentLifecycleObserver()
 {
 }
 
 } // namespace blink