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>
2 files changed