Revert "Remove Expect from core library."

tests/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.
 
 library EventTest;
-import "package:expect/expect.dart";
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 // TODO(nweiz): Make this private to testEvents when Frog supports closures with
 // optional arguments.
 eventTest(String name, Event eventFn(), void validate(Event),
     [String type = 'foo']) {
   test(name, () {
     final el = new Element.tag('div');
@@ skipping 206 matching lines @@
     expect(ev.metaKey, isTrue);
   }, type: 'mousewheel');
 
   // HttpRequestProgressEvent has no properties to itself, so just test that
   // it doesn't error out on creation and can be dispatched.
   // Issue 1005.
   // eventTest('HttpRequestProgressEvent',
   //     () => new HttpRequestProgressEvent('foo', 5),
   //     (ev) {});
 }