New helper for creating a color space from another, with linear gamma

Going to need this in many places once we expliclty require F16 surfaces
to have linear gamma color spaces.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2270103002

Review-Url: https://codereview.chromium.org/2270103002
2 files changed