Test CodecImageGenerator on GPU bots

Test CodecImageGenerator on GPU bots

In crrev.com/1549473003, CodecImageGenerator implemented getYUV8Planes,
so that we can test on a GPU bot. Update the arguments to DM so that
we run CodecImageGenerator on GPU bots.

This is adapted from:
https://codereview.chromium.org/1663453002/

This will cause many untriaged images on Gold.
The GPU converts YUV->RGBA differently than we
do in software.

BUG=skia:4888
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1676663002

Review URL: https://codereview.chromium.org/1676663002