Chrome Version: Not sure - I believe I have seen this on Canary.

What steps will reproduce the problem?
(1) It's hard for me to reliably repro but I think it happens after I've updated my device.
(2) Update device
(3) Enter password
(4) Hit enter to sign in

What is the expected result?
Device moves from sign in screen to unlocked device smoothly.

What happens instead?
A black square flashes briefly over the pod right before the device unlocks. 

zalcorn@ saw this when signing in to multi-profile also.