SkMixerColorFilter GPU impl

Bug: skia:
Change-Id: Ia1e25e0c99737d9720c17f92f0d76a1cb7897ea8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/193163
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
7 files changed