It can sometimes be difficult for child actors to shed public conceptions of them as a kid on screen, hindering these stars from being taken seriously in Hollywood as adults. But at 30, Dakota Fanning is feeling better than ever about her creative voice and agency and has found herself drawn to complicated characters. The realness of her character in “The Watchers,” a psychological horror fantasy film which hits theaters Friday, is part of what drew her to the role, something she and director Ishana Night Shyamalan bonded over.