When both scroll bar's policies are set to ScrollBarAsNeeded, make sure
the scroll bars are shown if needed and not show if not. Even the corner
case, where one scroll bar's visibility depends on the other, is handled
properly.
Task-number: QTBUG-45470
Change-Id: I11d6ccf7c0b51644a5ce2d5c3fc59e2e4812755d
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>
Reviewed-by: Thorbjørn Lindeijer <bjorn@lindeijer.nl>
52c122e616