Add stack rewind to the RP builder.

Immediately before any backwards jumps, we now rewind the stack.
This ensures that long-running loops don't use an unbounded amount
of stack space.

Change-Id: I7cfb5a2de13859c22762c842c9b1cf8ce2e22688
Bug: skia:13676
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/616336
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed