Implement contextmenu attribute with basic support of <menu>

Source/core/html/CustomContextMenuProvider.cpp

Index: Source/core/html/CustomContextMenuProvider.cpp
diff --git a/Source/core/html/CustomContextMenuProvider.cpp b/Source/core/html/CustomContextMenuProvider.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..88648b22d4eb8ae2262ea9c1dc3db174eae066aa
--- /dev/null
+++ b/Source/core/html/CustomContextMenuProvider.cpp
@@ -0,0 +1,28 @@
+// 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/CustomContextMenuProvider.h"
+
+#include "core/html/HTMLMenuElement.h"
+#include "platform/ContextMenu.h"
+
+namespace WebCore {
+
+void CustomContextMenuProvider::populateContextMenu(ContextMenu* menu)
+{
+    for (size_t i = 0; i < m_items.size(); ++i)
+        menu->appendItem(m_items[i]);
+}
+
+void CustomContextMenuProvider::contextMenuItemSelected(const ContextMenuItem* item)
+{
+    if (m_menu) {
+        if (HTMLElement* element = m_menu->selectedMenuItem(item->action()))
+            element->click();
+    }
+}
+
+} // namespace