On Windows, service_manager is a scheduled task [1] [2] that runs start_service_manager.py [3] that runs service_manager.

[1] https://chrome-internal.googlesource.com/infra/puppet/+/master/puppetm/etc/puppet/modules/chrome_infra/manifests/service_manager/windows.pp
[2] https://chrome-internal.googlesource.com/infra/puppet/+/master/puppetm/etc/puppet/modules/chrome_infra/manifests/win_startup_task.pp
[3] https://chrome-internal.googlesource.com/infra/puppet/+/master/puppetm/etc/puppet/modules/chrome_infra/files/service_manager/start_service_manager.py

Investigate whether it's possible to run it as a real Windows service instead.