Add SkImage_GpuYUVA

Bug: skia:7903
Change-Id: I06edc155b0a0a0697dc0d0aab74b6876d631ca0d
Reviewed-on: https://skia-review.googlesource.com/156942
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
5 files changed