Remove deprecated APIs.

lib/src/media_type.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 'package:collection/collection.dart';
 import 'package:string_scanner/string_scanner.dart';
 
 import 'case_insensitive_map.dart';
 import 'scan.dart';
 import 'utils.dart';
@@ skipping 35 matching lines @@
     return wrapFormatException("media type", mediaType, () {
       var scanner = new StringScanner(mediaType);
       scanner.scan(whitespace);
       scanner.expect(token);
       var type = scanner.lastMatch[0];
       scanner.expect('/');
       scanner.expect(token);
       var subtype = scanner.lastMatch[0];
       scanner.scan(whitespace);
 
-      var parameters = {};
+      var parameters = <String, String>{};
       while (scanner.scan(';')) {
         scanner.scan(whitespace);
         scanner.expect(token);
         var attribute = scanner.lastMatch[0];
         scanner.expect('=');
 
         var value;
         if (scanner.scan(token)) {
           value = scanner.lastMatch[0];
         } else {
@@ skipping 74 matching lines @@
               value.replaceAllMapped(_escapedChar, (match) => "\\" + match[0]))
           ..write('"');
       } else {
         buffer.write(value);
       }
     });
 
     return buffer.toString();
   }
 }