VideoOutput: Take the surface's viewport into account

Task-Number: QTBUG-30410

Change-Id: I480ce0bcd7ec136e54b5bfc5fec0e901141b72d8
Reviewed-by: Josh Faust <jfaust@suitabletech.com>
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

src/imports/multimedia/qdeclarativevideooutput_window_p.h

@@ -62,6 +62,7 @@ public:
     void updateGeometry();
     QSGNode *updatePaintNode(QSGNode *oldNode, QQuickItem::UpdatePaintNodeData *data);
     QAbstractVideoSurface *videoSurface() const;
+    QRectF adjustedViewport() const Q_DECL_OVERRIDE;
 
 private:
     QPointer<QVideoWindowControl> m_videoWindowControl;