The Demon Barber of Fleet Street,” a remake of Stephen Sondheim Broadway musical about a murderous barber hell-bent on revenge, stars frequent Burton collaborators Johnny Depp and Helena Bonham Carter in roles many people have yet to see — singers. Helena Bonham Carter and Tim Burton have welcomed their second child, a girl, in London, the actress’ representative told a magazine. The star and director of the upcoming musical film “Sweeney Todd” are “absolutely delighted,” Karon Maskill told People for a story posted Sunday on the magazine’s Web site.