Make new StreamController be async by default.

sdk/lib/io/string_transformer.dart

 // 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.
 
 part of dart.io;
 
 /**
  * String encodings.
  */
 class Encoding {
@@ skipping 168 matching lines @@
 
   Stream<List<int>> bind(Stream<String> stream) => _encoder.bind(stream);
 }
 
 
 // Utility function to synchronously decode a list of bytes.
 String _decodeString(List<int> bytes, [Encoding encoding = Encoding.UTF_8]) {
   if (bytes.length == 0) return "";
   var string;
   var error;
-  var controller = new StreamController();
+  var controller = new StreamController(sync: true);
   controller.stream
     .transform(new StringDecoder(encoding))
     .listen((data) => string = data,
             onError: (e) => error = e);
   controller.add(bytes);
   controller.close();
   if (error != null) throw error;
   assert(string != null);
   return string;
 }
 
 
 // Utility function to synchronously decode a utf8-encoded list of bytes,
 // throwing on error.
 String _decodeUtf8Strict(List<int> bytes) {
   if (bytes.length == 0) return "";
   var string;
   var error;
-  var controller = new StreamController();
+  var controller = new StreamController(sync: true);
   controller.stream
     .transform(new Utf8DecoderTransformer(null))
     .listen((data) => string = data,
             onError: (e) => error = e);
   controller.add(bytes);
   controller.close();
   if (error != null) throw error;
   assert(string != null);
   return string;
 }
 
 
 // Utility function to synchronously encode a String.
 // Will throw an exception if the encoding is invalid.
 List<int> _encodeString(String string, [Encoding encoding = Encoding.UTF_8]) {
   if (string.length == 0) return [];
   var bytes;
-  var controller = new StreamController();
+  var controller = new StreamController(sync: true);
   controller.stream
     .transform(new StringEncoder(encoding))
     .listen((data) => bytes = data);
   controller.add(string);
   controller.close();
   assert(bytes != null);
   return bytes;
 }
 
 
@@ skipping 148 matching lines @@
 
 // Utility class for decoding Windows current code page data delivered
 // as a stream of bytes.
 class _WindowsCodePageDecoder extends StreamEventTransformer<List<int>, String> {
   void handleData(List<int> data, EventSink<String> sink) {
     sink.add(_decodeBytes(data));
   }
 
   external static String _decodeBytes(List<int> bytes);
 }