Chrome Version: 63.0.3236.0 (dev)
OS: ChromeOS Panther

What steps will reproduce the problem?
(1) Sign-in with a couple of profiles.
(2) Wait for the awesome ChromeOS team to push a new build.
(3) Clicky to restart and apply the new build.
(4) Sign-in the two profiles again.

What is the expected result?

Expect that the two profiles restore all their tabs.

What happens instead?

Both profiles bring up a single tab, with a "Restore tabs" prompt, indicating that the browser crashed, or corrupted the profiles in some way, while restarting to apply the update.