Qml Menu does not hide on 2nd click or when focus is lost on UWP / WinRT

Add a simple menu to the calendar exemple projet :

    [...]
    menuBar: MenuBar {
        id: m_nMenuBar

        Menu {
            title: "Menu"

            MenuItem {
                text: "Item"
            }
        }
    }
    [...]

What is expected :

• When I click on the menu "Menu", a list with "Item" shoudl be shown.
• When I click again on "Menu", it should disappear.
• When I click anywhere else that on the menu, the menu shoud disappear

What happens :

• When I click on the menu "Menu", a list with "Item" is shown.
• When I click again on "Menu", nothing happens.
• When I click anywhere else that on the menu, nothing happens.

Checkout Qt 5.8 from git : 10 nov / aba872f2dd1edcba9a850b963acfa9795e2e1aee