Bring back sRGB-write-control as a caps bit.

We're not going to support this on Vulkan (yet), but want to still
have it as an option for GL. (The fallback alternative for our YUV use
case involves injecting expensive fragment shader code, which we'd like
to avoid).

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1955603003

Review-Url: https://codereview.chromium.org/1955603003
4 files changed