Simplify ContextLifecycleNotifier's handling of ActiveDOMObjects.

Source/core/dom/ExecutionContext.cpp

 /*
  * 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 82 matching lines @@
     m_activeDOMObjectsAreSuspended = false;
     notifyResumingActiveDOMObjects();
 }
 
 void ExecutionContext::stopActiveDOMObjects()
 {
     m_activeDOMObjectsAreStopped = true;
     notifyStoppingActiveDOMObjects();
 }
 
-unsigned ExecutionContext::activeDOMObjectCount()
-{
-    return activeDOMObjects().size();
-}
-
 void ExecutionContext::suspendScheduledTasks()
 {
     suspendActiveDOMObjects();
     tasksWereSuspended();
 }
 
 void ExecutionContext::resumeScheduledTasks()
 {
     resumeActiveDOMObjects();
     tasksWereResumed();
@@ skipping 117 matching lines @@
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_pendingExceptions);
     visitor->trace(m_publicURLManager);
     HeapSupplementable<ExecutionContext>::trace(visitor);
 #endif
     ContextLifecycleNotifier::trace(visitor);
 }
 
 } // namespace blink