Color-correct Gray JPEG image decoding via ICC profiles.

SkColorSpace::MakeICC now parses Gray ICC profiles and
SkColorSpaceXform_A2B can now render color spaces from Gray ICC
profiles. This is not enabled for SkPngCodec as of right now as we don't
have any Gray PNG test images currently.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5214
CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD


Change-Id: Iea7136d1c163cd17cf0818af57f93efdbcb577e7
Reviewed-on: https://skia-review.googlesource.com/5214
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Robert Aftias <raftias@google.com>
4 files changed