Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/element_constructor_1_test.dart

 // Copyright (c) 2011, 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.
 
 // Put universally passing event constructors in this file.
 // Move constructors that fail on some configuration to their own
 // element_constructor_foo_test.dart file.
 
 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 main() {
   var isAnchorElement =
       predicate((x) => x is AnchorElement, 'is an AnchorElement');
   var isAreaElement =
       predicate((x) => x is AreaElement, 'is an AreaElement');
   var isDivElement = predicate((x) => x is DivElement, 'is a DivElement');
   var isCanvasElement =
       predicate((x) => x is CanvasElement, 'is a CanvasElement');
   var isParagraphElement =
@@ skipping 45 matching lines @@
   test('span', () {
       var e = new SpanElement();
       expect(e, isSpanElement);
     });
 
   test('select', () {
       var e = new SelectElement();
       expect(e, isSelectElement);
     });
 }