hide internals of SkColorMatrix (so we can migrate to col-major)

Change-Id: If0eb6fb2efb6816b92ad7ca7d8caaace71397b7f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/209409
Commit-Queue: Ravi Mistry <rmistry@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
10 files changed