Use Uint8List for byte lists in dart:convert.

runtime/lib/convert_patch.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.
 
 import "dart:typed_data";
 
 // JSON conversion.
 
 patch _parseJson(String json, reviver(var key, var value)) {
   _BuildJsonListener listener;
@@ skipping 557 matching lines @@
   }
 
   static double _parseDouble(String source, int start, int end)
       native "Double_parse";
 
   void fail(int position, [String message]) {
     if (message == null) message = "Unexpected character";
     throw new FormatException(message, source, position);
   }
 }
-
-// UTF-8 conversion.
-
-patch class _Utf8Encoder {
-  /* patch */ static List<int> _createBuffer(int size) => new Uint8List(size);
-}