In be268ae197 we made QCocoaWindow::setVisible
idempotent by checking if NSView.hidden needed update.
This failed to take into account the case when a window is moved from
being a child window to a top level, where the window is still visible
and the NSView's hidden state doesn't change, but we need to order in
the NSWindow that we're now managing.
We now check NSWindow.visible as well, if we're a top level window.
Pick-to: 6.5 6.6
Change-Id: I94434d6ebfe2c9ece6eac7f83f17ead250ccc07a
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>