Hollywood spent a decade asking if YouTube fame could translate to the box office. Lately, it has been getting a very loud answer. Take “Backrooms,” a psychological horror flick that A24 released in 3,400 theaters in the United States and Canada on Thursday. Directed by Kane Parsons — a 20-year-old first-time filmmaker whose videos have generated 342 million views on YouTube — “Backrooms” is on track to collect at least $60 million by the end of Sunday, according to box office analysts. To put