[chromium] more scripted workflows for janitor.json

[jankeromnes]

From this chromium-dev thread:

git cl upload -s -r reviewer@chromium.org --cc bystander@chromium.org --tbrs owner@chromium.org
git cl try
git cl try-results
git cl description
git cl comments
git cl set-commit
git cl web
git cl status
git cl issue
git cl help