Add StreamChannelTransformer.

test/stream_channel_test.dart

 // Copyright (c) 2016, 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:convert';
 import 'dart:isolate';
 
 import 'package:stream_channel/stream_channel.dart';
 import 'package:test/test.dart';
@@ skipping 26 matching lines @@
     expect(otherSinkController.stream.toList(), completion(equals([1, 2, 3])));
 
     otherStreamController.add(4);
     otherStreamController.add(5);
     otherStreamController.add(6);
     otherStreamController.close();
     expect(sinkController.stream.toList(), completion(equals([4, 5, 6])));
   });
 
   test("transform() transforms the channel", () {
-    var transformed = channel.transform(UTF8);
+    var transformed = channel.transform(
+        new StreamChannelTransformer.fromCodec(UTF8));
 
     streamController.add([102, 111, 111, 98, 97, 114]);
     streamController.close();
     expect(transformed.stream.toList(), completion(equals(["foobar"])));
 
     transformed.sink.add("fblthp");
     transformed.sink.close();
     expect(sinkController.stream.toList(),
         completion(equals([[102, 98, 108, 116, 104, 112]])));
   });
 }