Reland "Add support for do-while loops in PipelineStage."

This is a reland of 9c7e04cd6f372c100e7a46d86a8841dff0d368fa

The DeadReturnES3 test isn't enabled yet due to crashes in Radeon, but
the PipelineStage fixes need to be landed now.

Original change's description:
> Add support for do-while loops in PipelineStage.
>
> This allows us to run tests which use do-while loops (like
> DeadReturnES3) within dm.
>
> Change-Id: If8ecb6b3fcd23d79451a43edf8e1ee8a182de984
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/410459
> Commit-Queue: John Stiles <johnstiles@google.com>
> Auto-Submit: John Stiles <johnstiles@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Change-Id: I73715f09defd950156cc252be9a52a36620d6d5b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/410936
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
2 files changed