Change fromString constructor to parse static method

pkg/http/test/multipart_test.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.
 
 library multipart_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:utf';
 
@@ skipping 13 matching lines @@
 class _BodyMatches extends BaseMatcher {
   final String _pattern;
 
   _BodyMatches(this._pattern);
 
   bool matches(item, MatchState matchState) {
     if (item is! http.MultipartRequest) return false;
 
     var future = item.finalize().toBytes().then((bodyBytes) {
       var body = decodeUtf8(bodyBytes);
-      var contentType = new ContentType.fromString(
-          item.headers['content-type']);
+      var contentType = ContentType.parse(item.headers['content-type']);
       var boundary = contentType.parameters['boundary'];
       var expected = cleanUpLiteral(_pattern)
           .replaceAll("\n", "\r\n")
           .replaceAll("{{boundary}}", boundary);
 
       expect(body, equals(expected));
       expect(item.contentLength, equals(bodyBytes.length));
     });
 
     return completes.matches(future, matchState);
@@ skipping 180 matching lines @@
         content-type: application/octet-stream
         content-disposition: form-data; name="file"; filename="test-file"
 
         hello
         --{{boundary}}--
         '''));
       }), completes);
     });
   });
 }