Rename GrBatchAtlas -> GrDrawOpAtlas.

Change-Id: I776f37e42dcab8b16535c48df9c405b1f211f6c9
Reviewed-on: https://skia-review.googlesource.com/6165
Commit-Queue: Brian Salomon <brian@thesalomons.net>
Reviewed-by: Brian Osman <brianosman@google.com>
15 files changed