Make GrSurfaceProxy::Copy take SkBackingFit.

Change-Id: I492a685459a8a2e2a8074d3e504304a6e33dbd92
Reviewed-on: https://skia-review.googlesource.com/c/178938
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
6 files changed