Google Chrome < M72 - FileWriterImpl Use-After-Free

There's a use-after-free in the implementation of the FileWriter component of the mojo bindings for the filesystem API. The browser-process side of this API is defined in https://cs.chromium.org/chromium/src/thirdparty/blink/public/mojom/filesystem/filewriter.mojom?type=cs&sq=package:chromium&g=0...