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

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index 260a82307499ca8669b9e9e76bf570eeb1cedba8..b8ee1972e84aa50f41c2e9c9d885891ca1b7748c 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -254,6 +254,8 @@ public:
     DEFINE_ATTRIBUTE_EVENT_LISTENER(keypress);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(keyup);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(mousedown);
+    DEFINE_ATTRIBUTE_EVENT_LISTENER(mouseenter);
+    DEFINE_ATTRIBUTE_EVENT_LISTENER(mouseleave);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(mousemove);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(mouseout);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(mouseover);
@@ -659,7 +661,7 @@ public:
     void hoveredNodeDetached(Node*);
     void activeChainNodeDetached(Node*);
 
-    void updateHoverActiveState(const HitTestRequest&, Element*);
+    void updateHoverActiveState(const HitTestRequest&, Element*, const PlatformMouseEvent* = 0);
 
     // Updates for :target (CSS3 selector).
     void setCSSTarget(Element*);