Revert "Remove Expect from core library."

tests/corelib/queue_iterator_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 queue.iterator.test;
 
-import "package:expect/expect.dart";
 import 'dart:collection' show Queue;
 
 class QueueIteratorTest {
   static testMain() {
     testSmallQueue();
     testLargeQueue();
     testEmptyQueue();
   }
 
   static int sum(int expected, Iterator<int> it) {
@@ skipping 34 matching lines @@
     Iterator<int> it = queue.iterator;
     sum(0, it);
     Expect.isFalse(it.moveNext());
     Expect.isNull(it.current);
   }
 }
 
 main() {
   QueueIteratorTest.testMain();
 }