Los Angeles’ new mayor has vowed to help stanch the flow of film and TV production jobs out of Hollywood, starting with the appointment of a film czar at City Hall. But to make a real difference, Eric Garcetti needs to convince skeptical state pols to combat the lure of rich tax incentives from outside California. Two days after this year’s Oscars, Hollywood’s councilman Eric Garcetti, then running for mayor of Los Angeles, staged a media event at Sunset Gower Studios. Only a smattering of reporters and photographers showed up, perhaps because the gathering was to address “runaway production,” a...