use SkColorInfo in fm

Just refactoring code that predates SkColorInfo.

Change-Id: Iba5ffdf91e2e2517bf55ea8c5a36c4fe6583a6b3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376760
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed