J444 is JPeg YUV color space with 444 subsampling.
This implementation uses the existing I444ToARGB conversion, which is
BT.601 color space with 444 subsampling, but passing in the jpeg
color matrix constants.

TBR=harryjin@google.com
BUG=449

Review URL: https://codereview.chromium.org/1387313002 .