Remove deprecated APIs.

lib/src/authentication_challenge.dart

 // Copyright (c) 2015, 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:collection';
 
 import 'package:string_scanner/string_scanner.dart';
 
 import 'case_insensitive_map.dart';
 import 'scan.dart';
@@ skipping 24 matching lines @@
   /// Throws a [FormatException] if the header is invalid.
   static List<AuthenticationChallenge> parseHeader(String header) {
     return wrapFormatException("authentication header", header, () {
       var scanner = new StringScanner(header);
       scanner.scan(whitespace);
       var challenges = parseList(scanner, () {
         var scheme = _scanScheme(scanner, whitespaceName: '" " or "="');
 
         // Manually parse the inner list. We need to do some lookahead to
         // disambiguate between an auth param and another challenge.
-        var params = {};
+        var params = <String, String>{};
 
         // Consume initial empty values.
         while (scanner.scan(",")) {
           scanner.scan(whitespace);
         }
 
         _scanAuthParam(scanner, params);
 
         var beforeComma = scanner.position;
         while (scanner.scan(",")) {
@@ skipping 36 matching lines @@
 
   /// Parses a single WWW-Authenticate challenge value.
   ///
   /// Throws a [FormatException] if the challenge is invalid.
   factory AuthenticationChallenge.parse(String challenge) {
     return wrapFormatException("authentication challenge", challenge, () {
       var scanner = new StringScanner(challenge);
       scanner.scan(whitespace);
       var scheme = _scanScheme(scanner);
 
-      var params = {};
+      var params = <String, String>{};
       parseList(scanner, () => _scanAuthParam(scanner, params));
 
       scanner.expectDone();
       return new AuthenticationChallenge(scheme, params);
     });
   }
 
   /// Scans a single scheme name and asserts that it's followed by a space.
   ///
   /// If [whitespaceName] is passed, it's used as the name for exceptions thrown
@@ skipping 29 matching lines @@
     }
 
     scanner.scan(whitespace);
   }
 
   /// Creates a new challenge value with [scheme] and [parameters].
   AuthenticationChallenge(this.scheme, Map<String, String> parameters)
       : parameters = new UnmodifiableMapView(
             new CaseInsensitiveMap.from(parameters));
 }