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 size accordingly. Fixes an issue where black borders were added on top and bottom of fullscreen video.
Committed r202482: <http://trac.webkit.org/changeset/202482>