Fix tst_qgraphicsview::task255529_transformationAnchorMouseAndViewportMargins

If we do not process the event, q->underMouse may return false in
QGraphicsViewPrivate::centerView (as the QEvent::Enter has not been
received yet.)

It was working before if by luck, the window appears under the cursor.

Change-Id: I9b4497683eae20915680297013a9c21fd6275f4b
Reviewed-on: http://codereview.qt.nokia.com/2385
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@nokia.com>

tests/auto/qgraphicsview/tst_qgraphicsview.cpp

@@ -104,6 +104,7 @@ static void sendMouseMove(QWidget *widget, const QPoint &point, Qt::MouseButton
     QTest::mouseMove(widget, point);
     QMouseEvent event(QEvent::MouseMove, point, button, buttons, 0);
     QApplication::sendEvent(widget, &event);
+    QApplication::processEvents();
 }
 
 static void sendMouseRelease(QWidget *widget, const QPoint &point, Qt::MouseButton button = Qt::LeftButton)