Fix strong mode errors in dart:io.

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;
 
 /// The current system encoding.
 ///
 /// This us used for converting from bytes to/from String when
 /// communicating on stdin, stdout and stderr.
@@ skipping 44 matching lines @@
     return encoded;
   }
 
   /**
    * Starts a chunked conversion.
    */
   StringConversionSink startChunkedConversion(Sink<List<int>> sink) {
     return new _WindowsCodePageEncoderSink(sink);
   }
 
-  // Override the base-class' bind, to provide a better type.
-  Stream<List<int>> bind(Stream<String> stream) => super.bind(stream);
-
   external static List<int> _encodeString(String string);
 }
 
 class _WindowsCodePageEncoderSink extends StringConversionSinkBase {
   // TODO(floitsch): provide more efficient conversions when the input is
   // not a String.
 
   final Sink<List<int>> _sink;
 
   _WindowsCodePageEncoderSink(this._sink);
@@ skipping 29 matching lines @@
     return _decodeBytes(input);
   }
 
   /**
    * Starts a chunked conversion.
    */
   ByteConversionSink startChunkedConversion(Sink<String> sink) {
     return new _WindowsCodePageDecoderSink(sink);
   }
 
-  // Override the base-class' bind, to provide a better type.
-  Stream<String> bind(Stream<List<int>> stream) => super.bind(stream);
-
   external static String _decodeBytes(List<int> bytes);
 }
 
 class _WindowsCodePageDecoderSink extends ByteConversionSinkBase {
   // TODO(floitsch): provide more efficient conversions when the input is
   // a slice.
 
   final Sink<String> _sink;
 
   _WindowsCodePageDecoderSink(this._sink);
 
   void close() {
     _sink.close();
   }
 
   void add(List<int> bytes) {
     _sink.add(_WindowsCodePageDecoder._decodeBytes(bytes));
   }
 }