verify we check oldVisitCount and frecency = -1 everywhere we should be.
x)
MigrateV7Up() may need to call "rv =
prefs->SetIntPref(PREF_BROWSER_LEFTPANEFOLDERID, -1);"
covered by another bug, but we need to fix it before landing, otherwise going back and forth between versions will hork the organizer.
x)
