Revert "Remove Expect from core library."

tests/language/map_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.
 // A subtest of the larger MapTest. Will eliminate once the full
 // test is running.
 
-import "package:expect/expect.dart";
-
 class MapTest {
 
   static void testDeletedElement(Map map) {
     map.clear();
     for (int i = 0; i < 100; i++) {
       map[1] = 2;
       Expect.equals(1, map.length);
       int x = map.remove(1);
       Expect.equals(2, x);
       Expect.equals(0, map.length);
@@ skipping 195 matching lines @@
   static testMain() {
     test(new Map());
     testKeys(new Map());
   }
 }
 
 
 main() {
   MapTest.testMain();
 }