Polish the videowidget example.

- Add command line parsing and file argument.
- Port to Qt 5 connection syntax.
- Adapt size to available geometry (for High DPI).

Task-number: QTBUG-53114
Change-Id: I1c1c547ddb14210ef5900f99f4870d6d91b67088
Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>

examples/multimediawidgets/videowidget/videoplayer.h

@@ -50,6 +50,7 @@ QT_BEGIN_NAMESPACE
 class QAbstractButton;
 class QSlider;
 class QLabel;
+class QUrl;
 QT_END_NAMESPACE
 
 class VideoPlayer : public QWidget
@@ -59,6 +60,8 @@ public:
     VideoPlayer(QWidget *parent = 0);
     ~VideoPlayer();
 
+    void setUrl(const QUrl &url);
+
 public slots:
     void openFile();
     void play();