Version: 51.0.2704.79 beta (64-bit)
OS: Chrome OS

What steps will reproduce the problem?
(1) Sign into Profile A. Open browser.
(2) Sign into Profile B.

What is the expected output?
I'm now logged into Profile B, and do not see the browser from Profile A.

What do you see instead?
I see the browser window from Profile A and can interact with it. This is not 100% reproable, but happens pretty frequently. I've tried with 2 or 3 profiles, switching back and forth. The browser window is always from the primary profile (first one that was logged in).

I'm on first gen Pixel. Let me know if there's any other info I can provide.