Revert "Remove Expect from core library."

tests/language/param2_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.
 // Dart test program for testing function type parameters.
 
-import "package:expect/expect.dart";
-
 
 class Param2Test {
 
   static forEach(List<int> a, int f(k)) {
     for (int i = 0; i < a.length; i++) {
       a[i] = f(a[i]);
     }
   }
 
   static int apply(f(int k), int arg) {
@@ skipping 38 matching lines @@
 
     var isZero = (e) => e == 0;
     Expect.equals(false, exists(v, isZero));
   }
 }
 
 
 main() {
   Param2Test.testMain();
 }