It's the new user switcher. It used to be that you could create multiple chrome "users", and each one would have a different profile, cache, saved passwords, etc. Great feature for households with multiple people that shared a single computer. But most people didn't know about it and it was under utilized.
Previously, if you had multiple users, you would see a little avatar icon to the left of your leftmost tab, and clicking that would drop down a little bubble that would you let you change the active user on the fly. That has been moved to the place you see now, and I believe it now shows even if you are the only user, due to the addition of allowing you to go incognito. This is another useful feature that most people didn't know about or didn't understand, so they are trying to increase its visibility to make more people aware of it.
Any way to hide that thing? Not seeing an option for that in the settings.