Remove mutually exclusive comments and code from VpxVideoDecoder.

Code and comments say opposite things about which color space info
to prefer. Unify on the config only after checking with hubbe@ and
confirming that webm vp9.2 encodes do need to use the config color
space instead of bitstream.

BUG=none
TEST=hubbe@ && vp9.2 playback.

Change-Id: If990c79481eab3e6925c39b1457d182a7d1cbdbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1670122
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672723}
1 file changed