The switch to GrColorType does mean that we can no longer represent compressed backend formats in the Mock backend surfaces.
This will require a Chrome CL before it can land in Skia.
TBR=bsalomon@google.com
Change-Id: Ie4e2d4826f960664a21d3de79933eb1cb5d06896
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/225538
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
a5e78be278