This directory contains the renderer side implementation of various filesystem related APIs.
//storage/browser/file_system/ contains part of the browser side implementation, while //content/browser/fileapi/ contains the rest of the browser side implementation and blink/public/mojom/filesystem contains the mojom interfaces for these APIs.
First of all this directory contains the implementation of the Entries API. This API consists of types to expose read-only access to file and directory entries to the web, primarily used by drag-and-drop and <input type=file>. Our implementation doesn't match the interface names of the spec, but otherwise should be pretty close to the spec.
TODO(mek): More details
Secondly this directory contains the implementation of something similar to the deprecated w3c file-system-api. This API is very similar to the previous Entries API, but it also adds support for writing and modifying to files and directories, as well as a way to get access to a origin scoped sandboxed filesystem.
TODO(mek): More details