Fix SurfaceAsyncReadPixels test and non-scaled colorspace transforms.

CL https://skia-review.googlesource.com/c/skia/+/348886 did a refactor
which ended up breaking SurfaceAsyncReadPixels so it never executed
any readbacks. Subsequently, a follow-up CL
https://skia-review.googlesource.com/c/skia/+/405497 broke colorspace
conversion because it was never being tested.

This fixes the test, and restores the old way of managing colorspace
transforms. A later CL will handle the colorspace transform through
rescale as intended, now that it can be tested properly.

Change-Id: I96731bd18b1046014185f6f20d2edb2241e80bb7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/739077
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed