Extract an http_parser package from shelf.

pkg/http_parser/test/media_type_test.dart

Index: pkg/http_parser/test/media_type_test.dart
diff --git a/pkg/shelf/test/media_type_test.dart b/pkg/http_parser/test/media_type_test.dart
similarity index 98%
rename from pkg/shelf/test/media_type_test.dart
rename to pkg/http_parser/test/media_type_test.dart
index 382ea46c6b187243b1250f1ff18b60188a034f9d..14affbb3cc94ce3381cc1f6f26baf4482d3b4efc 100644
--- a/pkg/shelf/test/media_type_test.dart
+++ b/pkg/http_parser/test/media_type_test.dart
@@ -2,9 +2,9 @@
 // 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 shelf.media_type_test;
+library http_parser.media_type_test;
 
-import 'package:shelf/src/media_type.dart';
+import 'package:http_parser/http_parser.dart';
 import 'package:unittest/unittest.dart';
 
 void main() {