Remove Encoding-enum from dart:io and add interface in dart:convert.

utils/testrunner/layout_test_controller.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.
 
 // The following set of variables should be set by the caller that
 // #sources this file.
 /** Whether to include elapsed time. */
 
 part of test_controller;
 
@@ skipping 150 matching lines @@
     return exitCode;
   })
   .catchError((e) {
     stderr.add("#Error starting process $command: ${e.error}");
   });
 }
 
 void _pipeStream(Stream stream, List<String> destination,
                  Function outputMonitor) {
   stream
-      .transform(new StringDecoder())
+      .transform(UTF8.decoder)
       .transform(new LineTransformer())
       .listen((String line) {
         if (outputMonitor != null) {
           outputMonitor(line);
         }
         destination.add(line);
       });
 }
 
 /**
@@ skipping 177 matching lines @@
 
 void runPixelLayoutTests() {
   init();
   runPixelLayoutTest(0);
 }
 
 void runTextLayoutTests() {
   init();
   runTextLayoutTest(0);
 }