Make GrDrawAtlasOp a non-legacy GrMeshDrawOp

Change-Id: I4d517855dbe3ee6894d7d457e0fc4488f204300c
Reviewed-on: https://skia-review.googlesource.com/22542
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
6 files changed