[autoroll] Fix transition/loop, add logging
[autoroll] Fix transition/loop, add logging

This prevents us from looping forever, fixes one case of that,
and the logging will help debug slow or stuck transitions.

Bug: skia:
Change-Id: Idf390190ecad0586bb447366adaa39555e06c438
Reviewed-on: https://skia-review.googlesource.com/24084
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

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