Context Menu stay on top after change top level window using shortcuts

import QtQuick 2.1
import QtQuick.Controls 1.0
Item{
    Rectangle{
        anchors.fill: parent
    }
    MouseArea {
        anchors.fill: parent
        onClicked: contextMenu.popup()
        acceptedButtons: Qt.RightButton
        Menu{
            id:contextMenu;
            MenuItem{text:"Item 1"}
            MenuItem{text:"Item 2"}
        }
    } 
}