chromium/third_party/blink/renderer/core/streams/underlying_source_cancel_callback.idl

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// https://streams.spec.whatwg.org/#callbackdef-underlyingsourcecancelcallback

callback UnderlyingSourceCancelCallback = Promise<void> (optional any reason);