Revert "Remove Expect from core library."

tests/language/optional_named_parameters_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.
 // Dart test program for testing optional named parameters.
 
-import "package:expect/expect.dart";
-
 
 class OptionalNamedParametersTest {
 
   static int F00() {
     return 0;
   }
 
   int f11() {
     return 0;
   }
@@ skipping 80 matching lines @@
     Expect.equals(10253545, F41(10, d:45, c:35, b:25));
     Expect.equals(10253545, np.f52(10, d:45, c:35, b:25));
   }
 }
 
 main() {
   OptionalNamedParametersTest.test();
 }
 
 // TODO(regis): negative tests: [} {] [a:0] {a=0}