Revert "SkMixerColorFilter GPU impl"

This reverts commit e80f7eb9d6a15d42827108700990291d3efb5995.

Reason for revert: break crossfade in chrome roll?

Original change's description:
> 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>

TBR=bsalomon@google.com,ethannicholas@google.com,fmalita@chromium.org,reed@google.com

Change-Id: Ib9464fcabc649b95ba131146690d6208af728436
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/197760
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
7 files changed