Roll Observatory packages and add a roll script

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

Index: packages/async/lib/src/delegate/future.dart
diff --git a/packages/async/lib/src/delegate/future.dart b/packages/async/lib/src/delegate/future.dart
new file mode 100644
index 0000000000000000000000000000000000000000..34f615892a09d386275c0c62004349ebce885565
--- /dev/null
+++ b/packages/async/lib/src/delegate/future.dart
@@ -0,0 +1,28 @@
+// Copyright (c) 2015, 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.
+
+library async.delegate.future;
+
+import 'dart:async';
+
+/// A wrapper that forwards calls to a [Future].
+class DelegatingFuture<T> implements Future<T> {
+  /// The wrapped [Future].
+  final Future _future;
+
+  DelegatingFuture(this._future);
+
+  Stream<T> asStream() => _future.asStream();
+
+  Future catchError(Function onError, {bool test(error)}) =>
+    _future.catchError(onError, test: test);
+
+  Future then(onValue(T value), {Function onError}) =>
+    _future.then(onValue, onError: onError);
+
+  Future<T> whenComplete(action()) => _future.whenComplete(action);
+
+  Future timeout(Duration timeLimit, {void onTimeout()}) =>
+    _future.timeout(timeLimit, onTimeout: onTimeout);
+}