Remove unused 'offset' parameter from peekDstTexture.

The dest-texture uniforms are being set directly inside GrPipeline now;
our callers don't have any other reason to inspect the offset.

Change-Id: I319287cc26767a4ea294da6615e83168500b318f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/415876
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
3 files changed