There is a rotation of people who are tasked with helping maintain a healthy flow of versions of Chrome/Chromium into Chrome OS/Chromium OS.
Chrome on Chrome OS Gardening Duties:
1. Shadow Chromium sheriffs for Chromium OS-specific configurations.
2. Keep Chrome OS UI BVTs green.
3. Help fix the crashes labeled TreeCloser on the Chromium waterfall.
Chrome on Chrome OS gardening documentation