QWidget is polished when show() is called, so unless you do this
first, QWidget::font() will return a default constructed QFont,
and not necessarily the default specified in the platform theme.
Comparing this to QPainter::font() later, which has been resolved
against the platform theme font, and not the default constructed
font, you can get a mismatch and a false test failure. This
happened on Android.
Change-Id: I41ef5b10879bbd4bb8ef8d52ecaccf5e8e894075
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>