chrome://settings should allow duplicate profile names.
Since a profile name can be a Gaia name, we can't really have this
distinction around anymore (people can sign in to two different profiles with
accounts that have the same Gaia name. Since that's allowed, then
the UI should allow this too)
BUG=445037
TEST=Go to chrome://settings and try to rename a profile to an already existing
profile's name. The UI should allow that.
Review URL: https://codereview.chromium.org/
834673005
Cr-Commit-Position: refs/heads/master@{#310112}