DocumentsProvider is an API in Android to provide custom filesystem by App(https://developer.android.com/guide/topics/providers/document-provider.html?hl=ja),
like fileSystemProvider in ChromeOS(https://developer.chrome.com/apps/fileSystemProvider).

nya@ is working on introducing "recent" file system(https://bugs.chromium.org/p/chromium/issues/detail?id=739398) and media sharing(go/arc++mediaview). Those filesystems are implemented with DocumentsProvider.

One of my intern project is exposing 3rd party DocumentsProvider to users.

There might be some UX problems:

 - Should we display those filesystems as users can guess those are from Android, not Chrome.
    - If a user installs the same app in both chrome and android, it might be confusing if there are same icon on  Files app.
 - Should we allow users to write/delete/modify files?