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

Source/core/dom/EventTarget.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, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 103 matching lines @@
         virtual bool dispatchEvent(PassRefPtr<Event>);
         bool dispatchEvent(PassRefPtr<Event>, ExceptionCode&); // DOM API
         virtual void uncaughtExceptionInEventHandler();
 
         // Used for legacy "onEvent" attribute APIs.
         bool setAttributeEventListener(const AtomicString& eventType, PassRefPtr<EventListener>, DOMWrapperWorld* isolatedWorld = 0);
         EventListener* getAttributeEventListener(const AtomicString& eventType, DOMWrapperWorld* isolatedWorld = 0);
 
         bool hasEventListeners();
         bool hasEventListeners(const AtomicString& eventType);
+        bool hasCapturingEventListeners(const AtomicString& eventType);
         const EventListenerVector& getEventListeners(const AtomicString& eventType);
 
         bool fireEventListeners(Event*);
         bool isFiringEventListeners();
 
     protected:
         virtual ~EventTarget();
         
         virtual EventTargetData* eventTargetData() = 0;
         virtual EventTargetData* ensureEventTargetData() = 0;
@@ skipping 56 matching lines @@
     }
 
     inline bool EventTarget::hasEventListeners(const AtomicString& eventType)
     {
         EventTargetData* d = eventTargetData();
         if (!d)
             return false;
         return d->eventListenerMap.contains(eventType);
     }
 
+    inline bool EventTarget::hasCapturingEventListeners(const AtomicString& eventType)
+    {
+        EventTargetData* d = eventTargetData();
+        if (!d)
+            return false;
+        return d->eventListenerMap.containsCapturing(eventType);
+    }
+
 } // namespace WebCore
 
 #endif // EventTarget_h