GitLab

VideoDecoderVpx has supported VP9 for a while, but was missing a colour
conversion codepath from I444 frames to ARGB.

BUG=377239,260879,134202

Review URL: https://codereview.chromium.org/300653002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272846 0039d316-1c4b-4281-b951-d872f2087c98