Refactored SkColorSpace_A2B to allow arbitrary ordering of elements

This is essential for representing non-lutAtoBType A2B tags such as
lut16Type, lut8Type, mpet. Parsing of A2B0 tags was also moved ahead
of the TRC/XYZ-matrix parsing, as profiles examined with both tags
either had the TRC/XYZ tags as a fall-back or were incorrectly displayed
if only the TRC/XYZ tags were used.

This was submitted alone to reduce CL size. Tests that will use these changes will be introduced in the subsequent CLs that add on lut8/16Type A2B0 parsing. We already have lut16Type test images and these have been tested locally, but require additional code not submitted yet for lut16Type ICC profile parsing and A2B colorspace xforms.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2444553002

Review-Url: https://codereview.chromium.org/2444553002
4 files changed