Implement contextmenu attribute with basic support of <menu>

Source/core/html/CustomContextMenuProvider.cpp

+// 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/events/EventDispatcher.h"
+#include "core/events/MouseEvent.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)
+        return;
+
+    if (HTMLElement* element = m_menu->menuItemAt(item->action())) {
+        RefPtrWillBeRawPtr<SimulatedMouseEvent> click = SimulatedMouseEvent::create(EventTypeNames::click, m_menu->document().domWindow(), Event::create());
+        click->setRelatedTarget(m_menu->subjectElement());
+        EventDispatcher::dispatchEvent(element, EventDispatchMediator::create(click.release()));
+    }
+}
+
+} // namespace