Revert "Remove Expect from core library."

tests/corelib/apply_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.
 
-import "package:expect/expect.dart";
-
 // Testing Function.apply calls correctly.
 // This test is not testing error handling, only that correct parameters
 // cause a correct call.
 
 int test0() => 42;
 int test0a({int a}) => 37 + a;
 int test1(int i) => i + 1;
 int test1a(int i, {int a}) => i + a;
 int test2(int i, int j) => i + j;
 int test2a(int i, int j, {int a}) => i + j + a;
@@ skipping 55 matching lines @@
   // Test that apply works even with a different name.
   var app = confuse();
   Expect.equals(42, app(test2, [22, 20]));
 
   // Test that apply can itself be applied.
   Expect.equals(42, Function.apply(Function.apply, [test2, [17, 25]]));
 
   // Test that apply works on callable objects.
   testList(42, new Callable(), [13, 29]);
 }