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

Source/core/dom/ContextLifecycleObserver.h

 /*
  * Copyright (C) 2008 Apple 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.
  *
  */
 
 #ifndef ContextLifecycleObserver_h
 #define ContextLifecycleObserver_h
 
 #include "core/dom/ExecutionContext.h"
+#include "platform/LifecycleContext.h"
 
 namespace blink {
 
-template<> void observeContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
-template<> void unobserveContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
+template<> void observerContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
+template<> void unobserverContext(ExecutionContext*, LifecycleObserver<ExecutionContext>*);
 
 class ContextLifecycleObserver : public LifecycleObserver<ExecutionContext> {
 public:
     explicit ContextLifecycleObserver(ExecutionContext*, Type = GenericType);
     ExecutionContext* executionContext() const { return lifecycleContext(); }
 protected:
     virtual ~ContextLifecycleObserver();
 };
 
 } // namespace blink
 
 #endif // ContextLifecycleObserver_h