Add <menuitem>, new HTMLMenuElement IDL attributes.

Source/core/html/HTMLMenuItemElement.h

Index: Source/core/html/HTMLMenuItemElement.h
diff --git a/Source/core/html/HTMLMenuItemElement.h b/Source/core/html/HTMLMenuItemElement.h
new file mode 100644
index 0000000000000000000000000000000000000000..9ec14079f5bc56311055ba0bfe62301e32526874
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+++ b/Source/core/html/HTMLMenuItemElement.h
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef HTMLMenuItemElement_h
+#define HTMLMenuItemElement_h
+
+#include "core/html/HTMLElement.h"
+
+namespace blink {
+
+class HTMLMenuItemElement FINAL : public HTMLElement {
+public:
+    DECLARE_NODE_FACTORY(HTMLMenuItemElement);
+
+private:
+    explicit HTMLMenuItemElement(Document&);
+};
+
+} // namespace blink
+
+#endif