For use in scripts that check try job results, this is
currently practically the same as making requests to
https://codereview.chromium.org/api/<cl-number>/<patchset-number>.

However, I think that this might be more future-proof, since
it fetches try job information from Buildbucket, and I expect
to still work after migration from Rietveld to Gerrit.

BUG=640354

Review-Url: https://codereview.chromium.org/2274743003