Implement contextmenu attribute with basic support of <menu>

Source/core/html/HTMLMenuItemElement.cpp

Index: Source/core/html/HTMLMenuItemElement.cpp
diff --git a/Source/core/html/HTMLMenuItemElement.cpp b/Source/core/html/HTMLMenuItemElement.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..77000a5a63854fc9c079dc1b058ef6a1b0fa4b0d
--- /dev/null
+++ b/Source/core/html/HTMLMenuItemElement.cpp
@@ -0,0 +1,25 @@
+// 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.
+
+#include "config.h"
+#include "core/html/HTMLMenuItemElement.h"
+
+#include "core/HTMLNames.h"
+
+namespace WebCore {
+
+using namespace HTMLNames;
+
+inline HTMLMenuItemElement::HTMLMenuItemElement(Document& document)
+    : HTMLElement(menuitemTag, document)
+{
+    ScriptWrappable::init(this);
+}
+
+PassRefPtr<HTMLMenuItemElement> HTMLMenuItemElement::create(Document& document)
+{
+    return adoptRef(new HTMLMenuItemElement(document));
+}
+
+}