When turning off fullscreen mode and restoring the widget's geometry
we must inform the QWindow about the geometry change synchronously.
Otherwise QWidget::geometry() will return the old value.
Using the same technique for the state transition to fullscreen mode
without sending a separate resize event.
Autotest: tst_QWidget::saveRestoreGeometry
Task-number: QTBUG-26421
Change-Id: I869e36cd302d9a94e398f48949ab3cb7ee9cdf51
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>