It implements now this interface with its video-direction
property. Values are changed to GstVideoOrientationMethod but they have
the same value than the originals.
https://bugzilla.gnome.org/show_bug.cgi?id=768687
1. Otherwise rotating the video will clip and show black bars due to
gltransformation's implementation.
2. The other option of make gltransformation aspect-agnostic produces
incorrect output with perspective transformations.
