Update charted to 0.4.8 and roll

packages/async/lib/src/delegate/stream_sink.dart

Index: packages/async/lib/src/delegate/stream_sink.dart
diff --git a/packages/async/lib/src/delegate/stream_sink.dart b/packages/async/lib/src/delegate/stream_sink.dart
index b6ace650cb14c3d70a7ce711d8f1d890312c4d30..198df8a785dcfae6c0adf4c58194899505013a40 100644
--- a/packages/async/lib/src/delegate/stream_sink.dart
+++ b/packages/async/lib/src/delegate/stream_sink.dart
@@ -2,8 +2,6 @@
 // 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.
 
-library async.delegate.stream_sink;
-
 import 'dart:async';
 
 /// Simple delegating wrapper around a [StreamSink].
@@ -16,8 +14,18 @@ class DelegatingStreamSink<T> implements StreamSink<T> {
   Future get done => _sink.done;
 
   /// Create delegating sink forwarding calls to [sink].
-  DelegatingStreamSink(StreamSink sink)
-      : _sink = sink;
+  DelegatingStreamSink(StreamSink<T> sink) : _sink = sink;
+
+  DelegatingStreamSink._(this._sink);
+
+  /// Creates a wrapper that coerces the type of [sink].
+  ///
+  /// Unlike [new StreamSink], this only requires its argument to be an instance
+  /// of `StreamSink`, not `StreamSink<T>`. This means that calls to [add] may
+  /// throw a [CastError] if the argument type doesn't match the reified type of
+  /// [sink].
+  static StreamSink<T> typed<T>(StreamSink sink) =>
+      sink is StreamSink<T> ? sink : new DelegatingStreamSink._(sink);
 
   void add(T data) {
     _sink.add(data);