Implement contextmenu attribute with basic support of <menu>

Source/core/html/CustomContextMenuProvider.h

Index: Source/core/html/CustomContextMenuProvider.h
diff --git a/Source/core/html/CustomContextMenuProvider.h b/Source/core/html/CustomContextMenuProvider.h
new file mode 100644
index 0000000000000000000000000000000000000000..b00c4bf584c6f3bc5fc028f36bf3e8d69a51159a
--- /dev/null
+++ b/Source/core/html/CustomContextMenuProvider.h
@@ -0,0 +1,46 @@
+// 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 CustomContextMenuProvider_h
+#define CustomContextMenuProvider_h
+
+#include "core/page/ContextMenuProvider.h"
+#include "platform/ContextMenuItem.h"
+
+namespace WebCore {
+
+class ContextMenu;
+class HTMLMenuElement;
+
+class CustomContextMenuProvider FINAL : public ContextMenuProvider {
+public:
+    static PassRefPtr<CustomContextMenuProvider> create(HTMLMenuElement* menu, const Vector<ContextMenuItem>& items)
+    {
+        return adoptRef(new CustomContextMenuProvider(menu, items));
+    }
+
+private:
+    explicit CustomContextMenuProvider(HTMLMenuElement* menu, const Vector<ContextMenuItem>& items)
+        : m_menu(menu)
+        , m_items(items)
+    {
+    }
+
+    virtual ~CustomContextMenuProvider()
+    {
+    }
+
+    virtual void populateContextMenu(ContextMenu*) OVERRIDE;
+
+    virtual void contextMenuItemSelected(const ContextMenuItem*) OVERRIDE;
+
+    virtual void contextMenuCleared() OVERRIDE { }
+
+    RefPtr<HTMLMenuElement> m_menu;
+    Vector<ContextMenuItem> m_items;
+};
+
+} // namespace
+
+#endif