Sounds like a corrupted upgrade - try removing Chrome and installing
it again after saving the profile data. Chrome is much like Firefox in
that all the settings, passwords, bookmarks etc are stored in a single
folder so saving that then removing / re-installing and copying back
the data in the old profile to the new one puts things back as they
were. If this deletes the button then the corruption is in the profile
so it's a bit more work to get things back to as they should be but
not impossible.

BTW - location of profile is ~/.config/google-chrome/Default and
you'll need to enable viewing of hidden files to see it.