Actually, it seems to be to implement the "Contacts API": https://bugzilla.mozilla.org/show_bug.cgi?id=857730 https://bugzilla.mozilla.org/show_bug.cgi?id=85773

Actually, it seems to be to implement the "Contacts API": https://bugzilla.mozilla.org/show_bug.cgi?id=857730 https://bugzilla.mozilla.org/show_bug.cgi?id=857730 https://hg.mozilla.org/mozilla-central/rev/1d77c3062662 https://hg.mozilla.org/mozilla-central/rev/1d77c3062662 Note that it's only enabled in Nightlies with no plans to ship.