Add SkRasterPipeline support to SkModeColorFilter.

The shader leaves its color in r,g,b,a, so to implement this color filter, we move {r,g,b,a} into {dr,dg,db,da}, then load the filter's color in {r,g,b,a}, then apply the xfermode as usual.

I've left a note about how we could sometimes cut a stage for some xfermodes.  Similarly we really only need to move_src_dst instead of swap_src_dst, but it seemed handy and less error prone to do a full two way swap.  As usual, we can always circle back and fine-tune these things if we want.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3243
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Change-Id: I928c0fb25236eb75cf238134c6bebb53af5ddf07
Reviewed-on: https://skia-review.googlesource.com/3243
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Matt Sarett <msarett@google.com>

0 files changed, 0 insertions, 0 deletions