Which Chromite branch should be updated (Leave blank for "master")?

Reason for restart (including CL link if possible): Add guado-accelerator release builder to the waterfall.  We would like to begin testing on Friday, so if it can be scheduled for Thursday (at the latest), that would be great.

https://chrome-internal-review.googlesource.com/#/c/chromeos/cros-signing/+/449744/
https://chrome-internal-review.googlesource.com/#/c/chromeos/crostools/+/449854/

Cc any users you'd like notified of the restart.

TROOPERS: please issue restart within a restart window (go/chrome-infra-cros-restart-windows).

For more information, see go/chrome-infra-doc-cros.)