Revert "Steps towards making the convert library strong-mode compliant."

sdk/lib/convert/encoding.dart

Index: sdk/lib/convert/encoding.dart
diff --git a/sdk/lib/convert/encoding.dart b/sdk/lib/convert/encoding.dart
index fd6f91fcd543415302a00a65c2740cad8365c577..696b5f0fcf750196d14ab8e61f117e428f8fe9cf 100644
--- a/sdk/lib/convert/encoding.dart
+++ b/sdk/lib/convert/encoding.dart
@@ -10,9 +10,6 @@ part of dart.convert;
 abstract class Encoding extends Codec<String, List<int>> {
   const Encoding();
 
-  ChunkedConverter<String, List<int>, String, List<int>> get encoder;
-  ChunkedConverter<List<int>, String, List<int>, String> get decoder;
-
   Future<String> decodeStream(Stream<List<int>> byteStream) {
     return byteStream
       .transform(decoder)