[VideoSink] Fix remaining stride issues with the YUV upload
[VideoSink] Fix remaining stride issues with the YUV upload

Rows are always a multiple of 4 in GStreamer buffers, fix the case where
the width of the video is not a multiple of 4.

lubosz/clutter-gst,skinkie/clutter-gst,lubosz/clutter-gst,GNOME/clutter-gst,GNOME/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,skinkie/clutter-gst,GNOME/clutter-gst,lubosz/clutter-gst,skinkie/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst