implemented metal gpu backend texture upload testing

Bug: skia:
Change-Id: Ia3af58a0710f7f9792b37682a3cc45dd14282b71
Reviewed-on: https://skia-review.googlesource.com/140248
Commit-Queue: Timothy Liang <timliang@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
11 files changed