Reland "Add GrDisableColorXPFactory::makeXferProcessor()"

This is a reland of 11157ef97ae2c5bf844ed6b7f4cbda829f5f24af

Original change's description:
> Add GrDisableColorXPFactory::makeXferProcessor()
> 
> This allows us to access the actual XP for working directly with
> pipelines.
> 
> Bug: skia:
> Change-Id: I71e7c2e9d69f464685e28b4f4a85847f0496b864
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208345
> Commit-Queue: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>

Bug: skia:
Change-Id: I185aeea1e5f7d95ff551163828508d622897061a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208683
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
2 files changed