This directory contains part of the browser side implementation of the native file system API.
See https://wicg.github.io/native-file-system/ for the spec for this API.
//storage/browser/fileapi/ contains the backend this API is built on top of,
blink/renderer/modules/native_file_system contains the renderer side implementation and
blink/public/mojom/native_file_system contains the mojom interfaces for these APIs.