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 cb4d0b6729c976483468a7331e8f5defc0fc4469..3d10d24a3fbe50d5c9603bff35703979ad74b8c3 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -247,6 +247,8 @@ 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);
@@ -641,7 +643,7 @@ 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*);