Add <menuitem>, new HTMLMenuElement IDL attributes.

Source/core/css/html.css

Index: Source/core/css/html.css
diff --git a/Source/core/css/html.css b/Source/core/css/html.css
index b1ad9ac08e36a6200c371329432854a6b2ad9f7e..995c863e8d9f54d30ed15f440c7a3e3653e0fb41 100644
--- a/Source/core/css/html.css
+++ b/Source/core/css/html.css
@@ -650,6 +650,10 @@ datalist {
     display: none
 }
 
+menuitem {

[tkent, 2014/08/11 01:58:32]

We can't add CSS rules for a runtime-enabled feature to html.css because the
rules are effective even if the feature is disabled.  Please refer to
RenderTheme::extraDefaultStyleSheet.

[pals, 2014/08/11 09:11:58]

Done.

+    display: none
+}
+
 area, param {
     display: none
 }