Move impl into SkColorFilterBase

No expected changes to results (or public call-sites)

Change-Id: Ia0c5cfe2dc3beda82d91454527eda2e68287afb6
Bug: skia:10426
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/298559
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
28 files changed