Few movie stars today win over critics and convey Old Hollywood glamour as effortlessly as Scarlett Johansson does, all while seemingly impervious to the industry’s convulsions. Now 40, she has been famous most of her life. She turned 10 the year her first movie, North, opened in 1994; four years later, she was upstaging Robert Redford in The Horse Whisperer. In the decades since, she starred in cult films and blockbusters, made a record with Pete Yorn and earned a couple of Oscar nominations. Between hits and misses, she also married three times (most recently to Colin Jost) and had...