read method
Implementation
Future<ReadResult> read() async {
final promise = js_util.callMethod(this, 'read', []);
final future = js_util.promiseToFuture(promise);
final result = await future;
final done = js_util.getProperty<bool>(result, 'done');
final value = js_util.getProperty<Uint8List?>(result, 'value');
return ReadResult(done, value);
}