Remove SkSurfaceProps gamma-correctness flag entirely.

This is no longer required - gamma-correctness is now just based on the
presence or absence of a color space.

Public API change is just removal of (unused) flag.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2188463002
TBR=bsalomon@google.com

Review-Url: https://codereview.chromium.org/2188463002
12 files changed