Revert "Remove Expect from core library."

tests/language/bad_named_parameters2_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 bad named parameters.
 
-import "package:expect/expect.dart";
-
 
 class BadNamedParameters2Test {
 
   int foo(int a) {
     // Although no optional named parameters are declared, we must check that
     // no named arguments are passed in, either here or in the resolving stub.
     return a;
   }
 
   static testMain() {
     BadNamedParameters2Test np = new BadNamedParameters2Test();
 
     // Verify that NoSuchMethod is called after an error is detected.
     bool caught;
     try {
       caught = false;
       // No formal parameter named b.
       np.foo(b:25);  /// static type warning
     } on NoSuchMethodError catch (e) {
       caught = true;
     }
     Expect.equals(true, caught);
   }
 }
 
 main() {
   BadNamedParameters2Test.testMain();
 }