Third small fragment from "Reduce dependence on GrSurface's origin field"

TBR=bsalomon@google.com
Change-Id: Ifae30beb333e9d668fa1378e332e8a4d063a371e
Reviewed-on: https://skia-review.googlesource.com/26348
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed