switch unique_ptr with deleter to GrMemoryPool

I switched GrOps from using GrOpMemoryPool to
GrMemoryPool, but I forgot to switch over the
GrOp::Owner. Make sure the GrOp::Owner works for
both new/delete and GrMemoryPool.

In addition, convert one last unique_ptr<GrOp> to
GrOp::Owner.

Change-Id: I660ad77bee0f060f263ff2ed07974afb83063441
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330097
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed