Make dart:convert strong mode clean.

sdk/lib/convert/codec.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;
 
 /**
  * A [Codec] encodes and (if supported) decodes data.
  *
  * Codecs can be fused. For example fusing [JSON] and [UTF8] produces
@@ skipping 66 matching lines @@
 /**
  * Fuses the given codecs.
  *
  * In the non-chunked conversion simply invokes the non-chunked conversions in
  * sequence.
  */
 class _FusedCodec<S, M, T> extends Codec<S, T> {
   final Codec<S, M> _first;
   final Codec<M, T> _second;
 
-  Converter<S, T> get encoder => _first.encoder.fuse(_second.encoder);
-  Converter<T, S> get decoder => _second.decoder.fuse(_first.decoder);
+  Converter<S, T> get encoder => _first.encoder.fuse/*<T>*/(_second.encoder);
+  Converter<T, S> get decoder => _second.decoder.fuse/*<S>*/(_first.decoder);
 
   _FusedCodec(this._first, this._second);
 }
 
 class _InvertedCodec<T, S> extends Codec<T, S> {
   final Codec<S, T> _codec;
 
   _InvertedCodec(Codec<S, T> codec) : _codec = codec;
 
   Converter<T, S> get encoder => _codec.decoder;
   Converter<S, T> get decoder => _codec.encoder;
 
   Codec<S, T> get inverted => _codec;
 }