Make ProcessorRefTests op be a non-legacy GrMeshDrawOp

Change-Id: I80f8a7bad1fb8d499a3fec879ddd29ebbefe1eb6
Reviewed-on: https://skia-review.googlesource.com/23324
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed