correctly show/hide when used inside shadow DOM

[Nicolai8]

fix for Dropdown is closing immediately when used inside Shadow DOM

[Nicolai8]

The problem were in test_active_click method.
When element is created inside of shadow dom the evt.target is not pointing to the correct element but to shadow root element.
So, to avoid this behaviour I changed .getRootNote() call instead of .ownerDocument for the element on which test_active_click handler is applied.