Revert "Remove Expect from core library."

tests/language/local_function2_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 testing closures.
 
-import "package:expect/expect.dart";
-
 typedef T F<T>(T t);
 
 class Parameterized<T> {
   Parameterized() { }
   T mul3(F f, T t) { return 3*f(t); }
   T test(T t) {
     return mul3((T t) { return 3*t; }, t);
   }
 }
 
@@ skipping 13 matching lines @@
 
   static testMain() {
     Expect.equals(3 + 33, f(3));
     Expect.equals(9.0, new Parameterized<double>().test(1.0));
   }
 }
 
 main() {
   LocalFunction2Test.testMain();
 }