The url itself is deterministic like:
  https://{internal|chromium}-cq-status.appspot.com/v2/patch-status/<GERRIT_HOST>-review.googlesource.com/<issue>/<patchset>

For example, 
  https://chromium-cq-status.appspot.com/v2/patch-status/skia-review.googlesource.com/4751/2

Ideally, URL would be shown only if CQ was ever triggered on a given patchset, but we can start with just always showing it.

This is a regression vs Rietveld, but totally Afterglow like.