Revert "Remove Expect from core library."

tests/language/closures_with_complex_params_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";
-
 // Tests for parsing closures with complex parameter types.
 
 main() {
   test1();
   test2();
   test3();
 }
 
 class Pair<A, B> {
   final A fst;
@@ skipping 34 matching lines @@
   var ap2 = (f(Pair<int, Pair<int, int> > pr1), Pair<int, Pair<int, int> > pr)
                  => f(pr) * 100;
 
   var e = new Pair<int, Pair<int, int>>(100, new Pair<int, int>(200, 300));
 
   Expect.equals(2010, ap1(f1, e));
   Expect.equals(2020, ap1(f2, e));
   Expect.equals(20100, ap2(f1, e));
   Expect.equals(20200, ap2(f2, e));
 }