Charlie Chaplin and Buster Keaton were giants of the Silent Screen. Writers, producers, directors and stars of their own films, they spoke a language before The Talkies which stressed the physical over the verbal. Keaton and Chaplin’s careers overlapped, but Chaplin’s lasted longer. He was making films to the bloody end. But “The Great Stone Face,” as Keaton was known, created a celluloid template from which Chaplin drew inspiration. Their backgrounds, temperaments, and results differed, but both men were intrigued at turning their comedic gifts to boxing while the sport still mattered. Keaton was first out of the gate in 1926 with “Battling Butler,” a potboiler in which a skinny guy facing a bruiser is scared to death. Chaplin followed suit with his masterpiece “City Lights” in 1931. His parody of the sport is flawless. Boxing is no laughing matter, were it not for slapstick, were it not for old masters.