Fix subscription handling in stream decoder

tests/standalone/io/string_transformer_test.dart

 // Copyright (c) 2012, 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";
 import "dart:io";
 import "dart:isolate";
 import "dart:utf";
 
 void testUtf8() {
@@ skipping 203 matching lines @@
   var controller = new StreamController();
   controller.add(new String.fromCharCodes(data));
   controller.close();
   var stream = controller.stream
     .transform(new StringEncoder(Encoding.ISO_8859_1));
   stream.listen(
     (s) {
       Expect.fail("data not expected");
     },
     onError: (error) {
-    print(error);
       Expect.isTrue(error.error is FormatException);
     });
 
 }
 
 main() {
   testUtf8();
   testLatin1();
   testAscii();
   testReadLine1();
   testReadLine2();
   testErrorHandler();
   testLatin1EncoderError();
 }