Maybe Goldeneye stats can be useful:
https://cros-goldeneye.corp.google.com/chromeos/console/listCrosbolt?baselineMilestoneChannel=55%20%3A%20BETA&analysisType=RAW_VALUES&selectedDevices

Especially interesting boards: chell, lulu, elm

(1) go to https://chromeperf.appspot.com/report
(2) click sign in in the upper right (might not strictly be necessary)
(3) set testsuite to build_RootFilesystemSize
(4) pick all the bots
(5) set subtest to bytes_rootfs_prod
(6) wait for the graphs to show up

Problem: No way to track partition sizes (but doable?).

https://chromeperf.appspot.com/report?sid=dcea3ebf88d8e435a2b4aa5cc431746b3a30a24afe2b97a965ffee4104e63039

Take-away:
- Test images are only marginally bigger than prod image.
- There has been a large cut in Dec 2016 that reduced sizes by about 80 MB.
Thus, we should fit!

Steps (1)-(6) courtesy of Mike Frysinger:
https://groups.google.com/a/google.com/forum/#!topic/chromeos-team/Nj3UoaAWDMg

I'll keep this around until Chromad is enabled for ARM and 32bit x86, but at the moment it seems that there's nothing we need to do here.