GitLab

BUG=423049
TEST=Start Chrome with an empty user data dir and --enable-new-avatar-menu.
From the avatar menu, click on "Switch Person", and "Browse as Guest" from
the user manager. Without closing any of the profile windows, choose "Exit"
from the Guest profile's hot dog menu. Restart Chrome. It should start up
and reopen the previous non-guest opened profile.

Review URL: https://codereview.chromium.org/661603007

Cr-Commit-Position: refs/heads/master@{#300153}