CachedFileSystem

[jvilk]

A CachedFileSystem wraps a cache file system and a backing file system, and caches the backing file system's content into the cache file system according to a customizable policy.

If the cache file system persists across page loads, its contents will be reused according to the specified policy.

The file system will be greatly useful for file systems that are backed by network storage (e.g. XMLHttpRequest and Dropbox) and by compressed files (e.g. ZipFS). It will also allow us to remove custom inflexible caching solutions currently deployed in e.g. the XMLHttpRequest file system.

[james-pre]

Closing since the proposal is being tracked in #191.