Clean up GrDrawOpAtlas (take 2)

Relanding all the things

TBR=jvanverth@google.com
Change-Id: Ie4ecdaee1c192c841817a54d64a9b3f70d28b28f
Reviewed-on: https://skia-review.googlesource.com/111360
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed