Implement 'mouseenter' and 'mouseleave' from DOM Level 3 Events.

Source/core/dom/EventListenerMap.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2011 Andreas Kling (kling@webkit.org)
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 32 matching lines @@
 class EventTarget;
 
 typedef Vector<RegisteredEventListener, 1> EventListenerVector;
 
 class EventListenerMap {
 public:
     EventListenerMap();
 
     bool isEmpty() const { return m_entries.isEmpty(); }
     bool contains(const AtomicString& eventType) const;
+    bool containsCapturing(const AtomicString& eventType) const;
 
     void clear();
     bool add(const AtomicString& eventType, PassRefPtr<EventListener>, bool useCapture);
     bool remove(const AtomicString& eventType, EventListener*, bool useCapture, size_t& indexOfRemovedListener);
     EventListenerVector* find(const AtomicString& eventType);
     Vector<AtomicString> eventTypes() const;
 
     void removeFirstEventListenerCreatedFromMarkup(const AtomicString& eventType);
     void copyEventListenersNotCreatedFromMarkupToTarget(EventTarget*);
 
@@ skipping 26 matching lines @@
     unsigned m_index;
 };
 
 #ifdef NDEBUG
 inline void EventListenerMap::assertNoActiveIterators() { }
 #endif
 
 } // namespace WebCore
 
 #endif // EventListenerMap_h