In August, a photo surfaced of a boy in an Afro wig with makeup-darkened skin standing in for 11-year-old African-American actor Keith L. Williams on the Vancouver set of “Good Boys,” a comedy about three sixth-graders who ditch school and wind up on a road trip. The image sparked online outrage, and Seth Rogen, one of the film’s producers, quickly apologized, declaring that on all future projects his team would “take every precaution to make sure something similar does not take place again.” It turned out that the boy in the makeup, reportedly the son of a stuntman, was African-American...