Make sure widget is polished before checking its font

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>

tests/auto/gui/painting/qpainter/tst_qpainter.cpp

@@ -730,6 +730,7 @@ void tst_QPainter::initFrom()
     pal.setColor(QPalette::Foreground, QColor(255, 0, 0));
     pal.setBrush(QPalette::Background, QColor(0, 255, 0));
     widget->setPalette(pal);
+    widget->show();
 
     QFont font = widget->font();
     font.setPointSize(26);