Make lists parsed by JSON untyped.

lib/json/json.dart

 // Copyright (c) 2011, 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.
 
 #library("json");
 
 // Pure Dart implementation of JSON protocol.
 
 /**
  * Utility class to parse JSON and serialize objects to JSON.
@@ skipping 378 matching lines @@
 
       case JsonToken.LBRACKET:
         return _parseList();
 
       default:
         throw 'Unexpected token: ${token}';
       }
   }
 
   _parseObject() {
-    Map<String, Object> object = new Map<String, Object>();
+    final object = {};
 
     _parseSequence(JsonToken.RBRACE, (JsonToken token) {
       _assertTokenKind(token, JsonToken.STRING);
       final String key = token.str;
 
       token = _tokenizer.next();
       _assertTokenKind(token, JsonToken.COLON);
 
       token = _tokenizer.next();
       final value = _parseValue(token);
 
       object[key] = value;
     });
 
     return object;
   }
 
   _parseList() {
-    List<Object> list = new List<Object>();
+    final list = [];
 
     _parseSequence(JsonToken.RBRACKET, (JsonToken token) {
       final value = _parseValue(token);
       list.add(value);
     });
 
     return list;
   }
 
   void _parseSequence(int endTokenKind, void parseElement(JsonToken token)) {
@@ skipping 163 matching lines @@
         });
         _sb.add('}');
         _seen.removeLast();
         return;
 
       default:
         throw const JsonUnsupportedObjectType();
     }
   }
 }