Well, Drano contains sodium hydroxide, a highly alkaline solution.
So, unless the film is well taped down with waterproof tape, it could very possibly melt the emulsion.
Now, Drano is a liquid, something hard to control.
I'm wondering if the same trick wouldn't work just as well with Easy-Off oven cleaner?
It's a foam, so no mess there. It also contains sodium hydroxide. It's designed to cut through even the toughest grime...