Fix color order for 565,4444, and I8 samplers.

10 GMs fixed on Linux/Win!

Also, don't unpremul I8 colors.  It's inconsistent with the other formats.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2166623002

Review-Url: https://codereview.chromium.org/2166623002
1 file changed