[graphite] Add a result param to graphite callbacks.

Bug: skia:12974
Change-Id: Ie10ef5c8ab4e04647233a6039d22a2eb6437d6bf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/526022
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
15 files changed