[Performance]: Bitmap Layer Cache

Shouldn't the Bitmap Layer Cache be an LRU aswell ? (make a common cache instead for Image and any other cacheble quantity ?)

A use case :

Suppose my background layer is rendered one using a bunch of circles and shapes that i rendered on the fly or like iOS 7 style frosty-blur, doing it one time is quite expensive (despite scaling), I'd to keep it cached now if multiple objects come and go on the top of the screen ultimately the background will be thrashed first.. which is bad, though this is just an edge case but if we use LRU for ImageCache why not keep this on the same ?