So a correction to my post, I thought the film on mine was slowly coming off, but I checked them out today and they are definitely not. They are still in perfect condition. I don't know why I thought they were, it must have been on another car.

 

I assume that the liquid-filled mirror glass is the auto-dimming kind. Both my side mirrors are of this type. My passenger side mirror looks as though it has a yellowish film that's peeling off, when in reality it's the glass peeling away from its backing, making the liquid inside become visible through the glass. It gets better, then worse, then better again, and so on. Hope that made sense to everyone.