change drawAtlas to behave like drawVertices

Bug: skia:6571
Change-Id: If60c30755ec0548df0e9bdeca2f3af0bc87764ca
Reviewed-on: https://skia-review.googlesource.com/14642
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed