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..b303651deaf6f41ab5a13ace77f0b99028aab350
--- /dev/null
+++ b/Source/core/html/HTMLMenuItemElement.cpp
@@ -0,0 +1,20 @@
+// 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 blink {
+
+inline HTMLMenuItemElement::HTMLMenuItemElement(Document& document)
+    : HTMLElement(HTMLNames::menuitemTag, document)
+{
+    ScriptWrappable::init(this);
+}
+
+DEFINE_NODE_FACTORY(HTMLMenuItemElement)
+
+} // namespace blink