Separate our use of sampler object from GL support.

When sampler objects exist but we're not using them we bind 0.

Speculatively disable use on ANGLE to see effect on performance.

Change-Id: I5c76bd812760a5ac67a4327f2d02f4f831155029

Bug: skia:10644
Change-Id: I7ef23704b2ca11d92806f196589ec561a3ac9435
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/314462
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed