Simplify lifecycle notifiers and observers.

Source/core/dom/ExecutionContext.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 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
@@ skipping 11 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 ExecutionContext_h
 #define ExecutionContext_h
 
 #include "core/dom/ContextLifecycleNotifier.h"
+#include "core/dom/ContextLifecycleObserver.h"
 #include "core/dom/SecurityContext.h"
 #include "core/fetch/AccessControlStatus.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 #include "platform/weborigin/KURL.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
@@ skipping 123 matching lines @@
     // Counter that keeps track of how many window interaction calls are allowed
     // for this ExecutionContext. Callers are expected to call
     // |allowWindowInteraction()| and |consumeWindowInteraction()| in order to
     // increment and decrement the counter.
     int m_windowInteractionTokens;
 };
 
 } // namespace blink
 
 #endif // ExecutionContext_h