When playing a 1280x720 video fullscreen on a monitor with the same resolution we should see the video fullscreen without top/bottom black bars.
It seems this regression was added in r201076.
Created attachment 281725 [details]
[GStreamer] Trigger video resize upon first sample rendering
The natural video size calculation depends on the validity of the
current sample, so whenever the first sample reached the sink it's a
good idea to reflect this on the player which will update its natural
Fixes an issue where black borders were added on top and bottom of
Committed r202482: <http://trac.webkit.org/changeset/202482>