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

This reverts commit 9c7e04cd6f372c100e7a46d86a8841dff0d368fa.

Reason for revert: ANGLE bots don't like it:
https://logs.chromium.org/logs/skia/53a05ed157eb6c11/+/steps/dm/0/stdout
Exception in SkSLDeadReturnES3_GPU

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>

TBR=brianosman@google.com,ethannicholas@google.com,johnstiles@google.com

Change-Id: Ib8ca1fd28b49c5e7d72290132336252218caac18
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/410779
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
2 files changed