Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/event_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.
 
 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 eventTest(String name, Event eventFn(), void validate(Event),
     [String type = 'foo']) {
   test(name, () {
     final el = new Element.tag('div');
     var fired = false;
     el.on[type].listen((ev) {
       fired = true;
       validate(ev);
     });
@@ skipping 166 matching lines @@
     expect(ev.screen.x, 3);
     expect(ev.screen.y, 4);
     expect(ev.client.x, 5);
     expect(ev.client.y, 6);
     expect(ev.ctrlKey, isTrue);
     expect(ev.altKey, isTrue);
     expect(ev.shiftKey, isTrue);
     expect(ev.metaKey, isTrue);
   }, 'mousewheel');
 }