Enable gpusrgb config on bots.

Don't run the config if we can't get a context with srgb support.
Includes a unit test for that logic.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1846603002

Review URL: https://codereview.chromium.org/1846603002
6 files changed