implemented copy surface as draw then blit for metal gpu backend

Bug: skia:
Change-Id: Ifa2d7ced7c22f74c2829d11b24557dbe851e3473
Reviewed-on: https://skia-review.googlesource.com/142691
Commit-Queue: Timothy Liang <timliang@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
6 files changed