Rename GrOp::draw to GrOp::execute

Change-Id: I36b8532c57d0b6004a5fd283e30a506df89a4fa6
Reviewed-on: https://skia-review.googlesource.com/6387
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
14 files changed