Revert "Remove Expect from core library."

tests/compiler/dart2js_extra/for_in_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";
-
 // Test foreach (aka. for-in) functionality.
 
 testIterator(List expect, Iterable input) {
   int i = 0;
   for (var value in input) {
     Expect.isTrue(i < expect.length);
     Expect.equals(expect[i], value);
     i += 1;
   }
   Expect.equals(expect.length, i);
@@ skipping 57 matching lines @@
 
   // Using the same variable (showing that the expression is evaluated
   // in the outer scope).
   int result = 0;
   var x = [1,2,3];
   for (var x in x) {
     result += x;
   }
   Expect.equals(6, result);
 }