This reflects the API changes to the aom_codec_decode function and the removal of I440. It also sets allow_lowbitdepth to give proper support for 8 bit video, and removes the git version from the mime type.
The libaom av1 decoder will return 16 bit per channel aom_image_t structures with only 8 significant bits.
Detect this case and use the mSkip fields of PlanarYCbCrImage to handle the extra data instead of allocating and performing an extra copy to obtain the necessary 8 bit representation.
The libaom av1 decoder can return high bit depth frame data now. Handle those frames by downsampling them to 8 bits per channel so they can be passed to our normal playback pipeline.
When av1 video playback is enabled, declare it as supported in the webm container in MediaSource.IsTypeSupported.
Also support special mime types of the form video/webm; codecs=vp9.experimental.<git-commit-id> so test sites can verify playback support of particular encodings while the av1 bitstream is under development.
