There is support for all features of SkColorSpace_A2B.
Tests for these functionality were adapted from
the XYZ xform, plus a CLUT-specific test was added.
Shared functions used by both SkColorSpaceXform_XYZ and SkColorSpaceXform_A2B
have been moved into a shared header.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2449243003
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
Review-Url: https://codereview.chromium.org/2449243003