Make dart:convert strong mode clean.

runtime/lib/convert_patch.dart

 // Copyright (c) 2014, 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.
 
 import "dart:_internal" show POWERS_OF_TEN;
 
 // JSON conversion.
 
 patch _parseJson(String json, reviver(var key, var value)) {
   _BuildJsonListener listener;
   if (reviver == null) {
     listener = new _BuildJsonListener();
   } else {
     listener = new _ReviverJsonListener(reviver);
   }
   var parser = new _JsonStringParser(listener);
   parser.chunk = json;
   parser.chunkEnd = json.length;
   parser.parse(0);
   parser.close();
   return listener.result;
 }
 
 patch class Utf8Decoder {
   /* patch */
-  Converter<List<int>, dynamic> fuse(Converter<String, dynamic> next) {
+  Converter<List<int>, dynamic/*=T*/> fuse/*<T>*/(
+      Converter<String, dynamic/*=T*/> next) {
     if (next is JsonDecoder) {
-      return new _JsonUtf8Decoder(next._reviver, this._allowMalformed);
+      return new _JsonUtf8Decoder(next._reviver, this._allowMalformed)
+          as dynamic/*=Converter<List<int>, T>*/;
     }
     // TODO(lrn): Recognize a fused decoder where the next step is JsonDecoder.
-    return super.fuse(next);
+    return super.fuse/*<T>*/(next);
   }
 
   // Allow intercepting of UTF-8 decoding when built-in lists are passed.
   /* patch */
   static String _convertIntercepted(
       bool allowMalformed, List<int> codeUnits, int start, int end) {
     return null;  // This call was not intercepted.
   }
 }
 
-class _JsonUtf8Decoder extends
-    ChunkedConverter<List<int>, Object, List<int>, Object> {
+class _JsonUtf8Decoder extends Converter<List<int>, Object> {
   final _Reviver _reviver;
   final bool _allowMalformed;
 
   _JsonUtf8Decoder(this._reviver, this._allowMalformed);
 
   Object convert(List<int> input) {
     var parser = _JsonUtf8DecoderSink._createParser(_reviver, _allowMalformed);
     parser.chunk = input;
     parser.chunkEnd = input.length;
     parser.parse(0);
@@ skipping 1712 matching lines @@
     _parser.parse(start);
   }
 
   void close() {
     _parser.close();
     var decoded = _parser.result;
     _sink.add(decoded);
     _sink.close();
   }
 }