Respect xfer barriers in InstancedRendering::Op

Fixes a bug introduced when this Op stopped storing a GrPipeline.

Change-Id: I1a39814cebe18b321ea369f005bb7759f233cfe6
Reviewed-on: https://skia-review.googlesource.com/10804
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
7 files changed