Update charted to 0.4.8 and roll

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

Index: packages/async/lib/src/delegate/sink.dart
diff --git a/packages/async/lib/src/delegate/sink.dart b/packages/async/lib/src/delegate/sink.dart
index bb50da33972521ff47578bf255566f0262c683ee..7c68a0fbc65f070f7f21556b7b8cda017f54e5cd 100644
--- a/packages/async/lib/src/delegate/sink.dart
+++ b/packages/async/lib/src/delegate/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.sink;
-
 /// Simple delegating wrapper around a [Sink].
 ///
 /// Subclasses can override individual methods, or use this to expose only the
@@ -12,8 +10,18 @@ class DelegatingSink<T> implements Sink<T> {
   final Sink _sink;
 
   /// Create a delegating sink forwarding calls to [sink].
-  DelegatingSink(Sink sink)
-      : _sink = sink;
+  DelegatingSink(Sink<T> sink) : _sink = sink;
+
+  DelegatingSink._(this._sink);
+
+  /// Creates a wrapper that coerces the type of [sink].
+  ///
+  /// Unlike [new DelegatingSink], this only requires its argument to be an
+  /// instance of `Sink`, not `Sink<T>`. This means that calls to [add] may
+  /// throw a [CastError] if the argument type doesn't match the reified type of
+  /// [sink].
+  static Sink<T> typed<T>(Sink sink) =>
+      sink is Sink<T> ? sink : new DelegatingSink._(sink);
 
   void add(T data) {
     _sink.add(data);