add mixer colorfilter

BUG=skia:

Change-Id: Icbee96056b17c5396a9d3783055ddd0b7d4fd3ff
Reviewed-on: https://skia-review.googlesource.com/c/9514
Commit-Queue: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
4 files changed