GStreamer 1.0: show preroll frames.

We need to implement the show_frame() function from GstVideoSink, which
handles both preroll and normal frames, instead of just
GstBaseSink.render(), which is called only for normal frames.
This was changed for GStreamer 0.10 by 3b20608f.

Change-Id: I4823a575d499cd0d6f9f4cb62e0420e070a05214
Reviewed-by: Andrew den Exter <andrew.den.exter@qinetic.com.au>

src/multimedia/gsttools_headers/qgstvideorenderersink_p.h

@@ -153,7 +153,7 @@ private:
 
     static gboolean stop(GstBaseSink *sink);
 
-    static GstFlowReturn render(GstBaseSink *sink, GstBuffer *buffer);
+    static GstFlowReturn show_frame(GstVideoSink *sink, GstBuffer *buffer);
 
 private:
     QVideoSurfaceGstDelegate *delegate;