Chrome Version: 48.0.2564.116
Chrome OS Version: 7647.84.0 
Chrome OS Platform: Pixel
Network info: Wifi

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Clicked into the profile switcher and tried clicking  "sign in another user...
but it immediately crashed. I tried looking at about:crashes but don't see anything there :/

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)

100%

What is the impact to the user, and is there a workaround? If so, what is
it?

Can't add another user, no workarounds.