This fragment processor reads back the color from the destination
surface; you can then use it as an input to other fragment processors.
Change-Id: Ibfe01fa92cf043f31e8284b7c7ed6c3d284d6429
Bug: skia:12066
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/415158
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
