We want to let more people test swarming tryjobs before switching over, and so will initially announce them as an opt-in feature.

IE:
cros tryjob --swarming <blah blah>

This needs:
  Confidence in swarming builds.
  Confidence in new build details UI.
  Additional builders allocated.

We currently have these known issues:
   https://crbug.com/800562   (no usable build artifacts, no hwtesting)
   https://crbug.com/802923   (no email with tryjob results)

I consider these non-blocking, but they do need to be mentioned in the announcement.