This will allow incoming NV12 frames to be encodable by libvpx without
requiring a conversion to I420 before encoding. NV12 is supported in
libvpx https://chromium.googlesource.com/webm/libvpx/+/master/CHANGELOG
Bug: webrtc:11916
Change-Id: I30e9c42c0607bee07691930c0248921bba09134c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/183720
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@google.com>
Cr-Commit-Position: refs/heads/master@{#32061}
