Revert "Remove Expect from core library."

tests/language/named_parameters_passing_false_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";
-
 // Dart test program for testing named parameters with 'false' passed as an
 // argument.
 
 
 class TestClass {
   TestClass();
 
   bool method([bool value]) => value;
   bool method2({bool value}) => value;
 
@@ skipping 22 matching lines @@
   Expect.equals(false, TestClass.staticMethod(false));
   Expect.equals(false, TestClass.staticMethod2(value: false));
 
   Expect.equals(null, globalMethod());
   Expect.equals(null, globalMethod2());
   Expect.equals(true, globalMethod(true));
   Expect.equals(true, globalMethod2(value: true));
   Expect.equals(false, globalMethod(false));
   Expect.equals(false, globalMethod2(value: false));
 }