Disable output swizzling from GrDisableColorXP

This makes sure the final shader does not output a color.

Bug: skia:
Change-Id: I1e5299bb63391d6ff72598ed72fe4fb80b18fa07
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206352
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
6 files changed