Add transformer support to Converters.

sdk/lib/convert/utf.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.convert;
 
 /**
  * An instance of the default implementation of the [Utf8Codec].
  *
  * This instance provides a convenient access to the most common UTF-8
@@ skipping 82 matching lines @@
    * The converter works more efficiently if the given [sink] is a
    * [ByteConversionSink].
    */
   StringConversionSink startChunkedConversion(
       ChunkedConversionSink<List<int>> sink) {
     if (sink is! ByteConversionSink) {
       sink = new ByteConversionSink.from(sink);
     }
     return new _Utf8EncoderSink(sink);
   }
+
+  // Override the base-classes bind, to provide a better type.
+  Stream<List<int>> bind(Stream<String> stream) => super.bind(stream);
 }
 
 /**
  * This class encodes Strings to UTF-8 code units (unsigned 8 bit integers).
  */
 // TODO(floitsch): make this class public.
 class _Utf8Encoder {
   int _carry = 0;
   int _bufferIndex = 0;
   final List<int> _buffer;
@@ skipping 197 matching lines @@
   ByteConversionSink startChunkedConversion(
       ChunkedConversionSink<String> sink) {
     StringConversionSink stringSink;
     if (sink is StringConversionSink) {
       stringSink = sink;
     } else {
       stringSink = new StringConversionSink.from(sink);
     }
     return stringSink.asUtf8Sink(_allowMalformed);
   }
+
+  // Override the base-classes bind, to provide a better type.
+  Stream<String> bind(Stream<List<int>> stream) => super.bind(stream);
 }
 
 // UTF-8 constants.
 const int _ONE_BYTE_LIMIT = 0x7f;   // 7 bits
 const int _TWO_BYTE_LIMIT = 0x7ff;  // 11 bits
 const int _THREE_BYTE_LIMIT = 0xffff;  // 16 bits
 const int _FOUR_BYTE_LIMIT = 0x10ffff;  // 21 bits, truncated to Unicode max.
 
 // UTF-16 constants.
 const int _SURROGATE_MASK = 0xF800;
@@ skipping 151 matching lines @@
       }
       break loop;
     }
     if (expectedUnits > 0) {
       _value = value;
       _expectedUnits = expectedUnits;
       _extraUnits = extraUnits;
     }
   }
 }