Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/datalistelement_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() {
   var isDataListElement =
       predicate((x) => x is DataListElement, 'is a DataListElement');
 
   var div;
 
   setUp(() {
       div = new DivElement();
       document.body.append(div);
@@ skipping 38 matching lines @@
     }, expectation);
   });
 
   test('create', () {
     expect(() {
       var list = new DataListElement();
       expect(list, isDataListElement);
     }, expectation);
   });
 }