Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/cdata_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
 
 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 main() {
   test('remove', () {
     var div = new Element.html('<div>content</div>');
     var cdata = div.nodes[0];
     expect(cdata is CharacterData, true);
     expect(cdata, isNotNull);
     expect(div.innerHtml, 'content');
 
     cdata.remove();
     expect(div.innerHtml, '');
   });
 }