iOS 7 Chrome - Fixed position drawer doesn't stay at bottom when virtual keypad pops up
Position fixed bottom and position absolute bottom are an absolute nightmare on iOS and android devices, in my experience it's just not possible to get it to render consistently even across the most modern devices, let alone the older ones that dominate the market currently. So much so, that as a dev I would ask a designer to rethink the layout because of it. I believe it's called "sidestepping the turd".