Rename batch->op in GrOpList and subclasses

Change-Id: I9c82483c4ac0dc140fb1e5e3650d6ff1e5917e99
Reviewed-on: https://skia-review.googlesource.com/5646
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
9 files changed