Improve the error-propagation on socket streams

tests/standalone/io/http_server_socket_test.dart

Index: tests/standalone/io/http_server_socket_test.dart
diff --git a/tests/standalone/io/http_server_socket_test.dart b/tests/standalone/io/http_server_socket_test.dart
index 6a71fd808b9b148ff9c72e3928e4c306ad5cc209..13b92d8f2bdb24b4772c1074fdb2a284eb08c9bb 100644
--- a/tests/standalone/io/http_server_socket_test.dart
+++ b/tests/standalone/io/http_server_socket_test.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2013, 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.
 
@@ -16,6 +16,10 @@ class ExpectedDataOutputStream implements OutputStream {
     _onNoPendingWrites = callback;
   }
 
+  void set onClosed(void callback()) {
+    // Not used in test.
+  }
+
   void set onError(void callback(e)) {
     _onError = callback;
   }