Update charted to 0.4.8 and roll

packages/async/lib/src/utils.dart

Index: packages/async/lib/src/utils.dart
diff --git a/packages/async/lib/src/utils.dart b/packages/async/lib/src/utils.dart
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+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+
+/// A generic typedef for a function that takes one type and returns another.
+typedef F UnaryFunction<E, F>(E argument);
+
+/// A typedef for a function that takes no arguments and returns a Future or a
+/// value.
+typedef FutureOr<T> FutureOrCallback<T>();