shader dither in SkRPBlitter

Following up on old bugs... might as well get this going.

Convert SkRasterPipelineBlitter's dither approach to match
SkVMBlitter and the GPU backend by dithering just after the
color filter, instead of just before storing to memory.

Bug: skia:10000
Change-Id: I5271706f707f553ef54d72ef029fd43331c2e25e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/291876
Commit-Queue: Mike Reed <reed@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
1 file changed