Steps towards making the convert library strong-mode compliant.

sdk/lib/convert/base64.dart

Index: sdk/lib/convert/base64.dart
diff --git a/sdk/lib/convert/base64.dart b/sdk/lib/convert/base64.dart
index c6cac6ed76cf42f1d7641cebbef604f7de72eb13..ff3a43959e1074818c120cbaa56c13f604357ca7 100644
--- a/sdk/lib/convert/base64.dart
+++ b/sdk/lib/convert/base64.dart
@@ -70,7 +70,8 @@ class Base64Codec extends Codec<List<int>, String> {
  *
  * The results are ASCII strings using a restricted alphabet.
  */
-class Base64Encoder extends Converter<List<int>, String> {
+class Base64Encoder extends
+    ChunkedConverter<List<int>, String, List<int>, String> {
   final bool _urlSafe;
 
   const Base64Encoder() : _urlSafe = false;
@@ -89,14 +90,6 @@ class Base64Encoder extends Converter<List<int>, String> {
     }
     return new _AsciiBase64EncoderSink(sink, _urlSafe);
   }
-
-  Stream<String> bind(Stream<List<int>> stream) {
-    return new Stream<String>.eventTransformed(
-        stream,
-        (EventSink sink) =>
-            new _ConverterStreamEventSink<List<int>, String>(
-                this, sink));
-  }
 }
 
 /**
@@ -348,7 +341,9 @@ class _Utf8Base64EncoderSink extends _Base64EncoderSink {
  *
  * The encoding is required to be properly padded.
  */
-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]) {