Make convert library strong-mode compliant.

sdk/lib/convert/base64.dart

 // Copyright (c) 2015, 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 [Base64Codec].
  *
  * This instance provides a convenient access to
@@ skipping 35 matching lines @@
 // ------------------------------------------------------------------------
 // Encoder
 // ------------------------------------------------------------------------
 
 /**
  * Base-64 encoding converter.
  *
  * Encodes lists of bytes using base64 encoding.
  * The result are ASCII strings using a restricted alphabet.
  */
-class Base64Encoder extends Converter<List<int>, String> {
+class Base64Encoder extends
+    ChunkedConverter<List<int>, String, List<int>, String> {
+
   const Base64Encoder();
 
   String convert(List<int> input) {
     if (input.isEmpty) return "";
     var encoder = new _Base64Encoder();
     Uint8List buffer = encoder.encode(input, 0, input.length, true);
     return new String.fromCharCodes(buffer);
   }
 
   ByteConversionSink startChunkedConversion(Sink<String> sink) {
     if (sink is StringConversionSink) {
       return new _Utf8Base64EncoderSink(sink.asUtf8Sink(false));
     }
     return new _AsciiBase64EncoderSink(sink);
   }
-
-  Stream<String> bind(Stream<List<int>> stream) {
-    return new Stream<String>.eventTransformed(
-        stream,
-        (EventSink sink) =>
-            new _ConverterStreamEventSink<List<int>, String>(this, sink));
-  }
 }
 
 /**
  * Helper class for encoding bytes to BASE-64.
  */
 class _Base64Encoder {
   /** The RFC 4648 base64 encoding alphabet. */
   static const String _base64Alphabet =
       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
@@ skipping 208 matching lines @@
     if (buffer != null) {
       _sink.addSlice(buffer, 0, buffer.length, isLast);
     }
   }
 }
 
 // ------------------------------------------------------------------------
 // Decoder
 // ------------------------------------------------------------------------
 
-class Base64Decoder extends Converter<String, List<int>> {
+class Base64Decoder extends
+    ChunkedConverter<String, List<int>, String, List<int>> {
+
   const Base64Decoder();
 
   List<int> convert(String input, [int start = 0, int end]) {
     end = RangeError.checkValidRange(start, end, input.length);
     if (start == end) return new Uint8List(0);
     var decoder = new _Base64Decoder();
     Uint8List buffer = decoder.decode(input, start, end);
     decoder.close(input, end);
     return buffer;
   }
@@ skipping 386 matching lines @@
     end = RangeError.checkValidRange(start, end, string.length);
     if (start == end) return;
     Uint8List buffer = _decoder.decode(string, start, end);
     if (buffer != null) _sink.add(buffer);
     if (isLast) {
       _decoder.close(string, end);
       _sink.close();
     }
   }
 }