video-sink: add context field to GstClutterSinkRenderer
video-sink: add context field to GstClutterSinkRenderer

https://bugzilla.gnome.org/show_bug.cgi?id=712834

ystreet/clutter-gst,lubosz/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst