Revert "Have GrAtlasManager use legacy behavior"

This reverts commit 4b7b2ceb4ad93861c2ae6b4fabce13f187ec4b93.

Reason for revert: breaks intel 640 gpu bots in dftext gm for glthreading config

Original change's description:
> Have GrAtlasManager use legacy behavior
> 
> The old code would generate a 1024 x 2048 x 4 atlas given a
> max size of 4MiB. And, the plot sizes would be 256 x 256. This CL
> mimics that behavior.
> 
> Change-Id: Iae741d5409daa034c6c3086c8a09476fb343353d
> Reviewed-on: https://skia-review.googlesource.com/c/162321
> Commit-Queue: Herb Derby <herb@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,herb@google.com

Change-Id: I61c6dd0e88ac8953706c6cb11bdc1cb2daa95544
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/162440
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed