Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/element_types_test.dart

 // Copyright (c) 2012, 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:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 main() {
   group('supported_content', () {
     test('supported', () {
       expect(ContentElement.supported, true);
     });
   });
 
   group('supported_datalist', () {
     test('supported', () {
@@ skipping 54 matching lines @@
       expect(TemplateElement.supported, true);
     });
   });
 
   group('supported_track', () {
     test('supported', () {
       expect(TrackElement.supported, true);
     });
   });
 }