For Chinese audiences, the extras mown down in a screen war that never ends are a powerful reminder of Japan’s brutal 14-year occupation, the climax of more than a century of humiliation at the hands of foreign powers. Japanese foreign-policy scholars say more than 200 anti-Japanese films were made last year. This well-nursed grudge is now a combustible ingredient in the dangerous territorial dispute over a group of rocky islands in the East China Sea, the most serious row between the two Asian powers since Japan’s 1945 defeat.