SkColorMatrix cleanup

Remove the RGB/YUV helpers (use SkYUVMath instead), along with the
unused get20/set20.

Change-Id: Id83467a1b7f33657869e0a933af75387a4e36a88
Bug: skia:9543
Change-Id: Id83467a1b7f33657869e0a933af75387a4e36a88
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/252188
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
7 files changed