Revert "Revert "Clean up onTransferPixels""

Bug: skia:5126
Change-Id: Ia1eaef56cca266ad4c413e711e63646e913222be
Reviewed-on: https://skia-review.googlesource.com/20445
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
11 files changed