This extracts the logic for SkRuntimeEffect's one-at-a-time handling of
colors, and also makes it more capable. We can now execute color filters
that invoke children with literals, or with the results of other
children (eg, compose color filter).
Change-Id: I53c6db0316a7162c32f2a7b86b35c947cccb42ea
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/408117
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1042334c6e