implemented copy surface as draw for metal gpu backend

Bug: skia:
Change-Id: Ie61bd6ad9f288b8a025d44f887a0954101a7d710
Reviewed-on: https://skia-review.googlesource.com/142687
Commit-Queue: Timothy Liang <timliang@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
14 files changed