Revert "Remove Expect from core library."

tests/corelib/collection_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 collection_test;
 
-import "package:expect/expect.dart";
 import 'dart:collection' show Queue;
 
 class CollectionTest {
   CollectionTest(Collection collection) {
     testReduce(collection);
   }
 
   void testReduce(Collection collection) {
     Expect.equals(28, collection.reduce(0, (prev, element) => prev + element));
     Expect.equals(
@@ skipping 16 matching lines @@
 
   // Growable list.
   new CollectionTest(new List.from(TEST_ELEMENTS));
 
   // Set.
   new CollectionTest(new Set.from(TEST_ELEMENTS));
 
   // Queue.
   new CollectionTest(new Queue.from(TEST_ELEMENTS));
 }