Revert "Remove Expect from core library."

tests/language/call_through_getter_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.
 
-import "package:expect/expect.dart";
-
 // Tests that we can call functions through getters.
 
 const TOP_LEVEL_CONST = 1;
 const TOP_LEVEL_CONST_REF = TOP_LEVEL_CONST;
 const TOP_LEVEL_NULL = null;
 
 var topLevel;
 
 class CallThroughGetterTest {
 
@@ skipping 141 matching lines @@
   get z { _mark('z'); return 2; }
 
   _mark(m) { _order.write(m); return _order.toString(); }
   StringBuffer _order;
 
 }
 
 main() {
   CallThroughGetterTest.testMain();
 }