Remove Expect from core library.

tests/compiler/dart2js_extra/mirror_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 "package:expect/expect.dart";
 import 'dart:mirrors';
 
 import 'async_helper.dart';
 
 void test(void onDone(bool success)) {
   var now = new DateTime.now();
   InstanceMirror mirror = reflect(now);
   print('now: ${now}');
   print('mirror.type: ${mirror.type}');
   print('now.toUtc(): ${now.toUtc()}');
@@ skipping 15 matching lines @@
 
 The authors of this program are aware of these problems and have
 decided the thrill of using an experimental feature is outweighing the
 risks.  Furthermore, the authors of this program understand that
 long-term, to fix the problems mentioned above, mirrors may have
 negative impact on size and performance of Dart programs compiled to
 JavaScript.
 """);
   asyncTest(test);
 }