Reland "implemented GrMtlSampler for metal gpu backend"

This reverts commit 35f9637a78b8f070f24416e185495c21a28a092c.

Reason for revert: <Removed setting border color since we don't clamp to border anyway>

Original change's description:
> Revert "implemented GrMtlSampler for metal gpu backend"
>
> This reverts commit 93fa10fbbc74cae8e57291acfe0c6c06f4ba8ff7.
>
> Reason for revert: <Breaking build on macOS ver < 10.12>
>
> Original change's description:
> > implemented GrMtlSampler for metal gpu backend
> >
> > Bug: skia:
> > Change-Id: I936e5510e5ee146c0fc6bdbc0d5f5352359fbe7d
> > Reviewed-on: https://skia-review.googlesource.com/145893
> > Commit-Queue: Timothy Liang <timliang@google.com>
> > Reviewed-by: Greg Daniel <egdaniel@google.com>
>
> TBR=egdaniel@google.com,timliang@google.com
>
> Change-Id: I4184890610e3147abc63b7d9bdfa8ec8120a11ef
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:
> Reviewed-on: https://skia-review.googlesource.com/146580
> Reviewed-by: Timothy Liang <timliang@google.com>
> Commit-Queue: Timothy Liang <timliang@google.com>

Bug: skia:
Change-Id: Icbf31144cba79c621eff4741871d27172f1004b7
Reviewed-on: https://skia-review.googlesource.com/146581
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Timothy Liang <timliang@google.com>
3 files changed