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

Source/core/html/HTMLElement.cpp

Index: Source/core/html/HTMLElement.cpp
diff --git a/Source/core/html/HTMLElement.cpp b/Source/core/html/HTMLElement.cpp
index 44c61761328927813994fea5d6ced1dfb9099ef3..e94d821824c8c4304ccb672bf80dc6d56c171662 100644
--- a/Source/core/html/HTMLElement.cpp
+++ b/Source/core/html/HTMLElement.cpp
@@ -204,6 +204,8 @@ AtomicString HTMLElement::eventNameForAttributeName(const QualifiedName& attrNam
         attributeNameToEventNameMap.set(oncontextmenuAttr.localName(), eventNames().contextmenuEvent);
         attributeNameToEventNameMap.set(ondblclickAttr.localName(), eventNames().dblclickEvent);
         attributeNameToEventNameMap.set(onmousedownAttr.localName(), eventNames().mousedownEvent);
+        attributeNameToEventNameMap.set(onmouseenterAttr.localName(), eventNames().mouseenterEvent);
+        attributeNameToEventNameMap.set(onmouseleaveAttr.localName(), eventNames().mouseleaveEvent);
         attributeNameToEventNameMap.set(onmousemoveAttr.localName(), eventNames().mousemoveEvent);
         attributeNameToEventNameMap.set(onmouseoutAttr.localName(), eventNames().mouseoutEvent);
         attributeNameToEventNameMap.set(onmouseoverAttr.localName(), eventNames().mouseoverEvent);