Remove Expect from core library.

tests/language/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";
+
 // Dart test for testing for in on a list literal.
 
 class ForInTest {
 
   static testMain() {
     testSimple();
     testGenericSyntax1();
     testGenericSyntax2();
     testGenericSyntax3();
     testGenericSyntax4();
@@ skipping 28 matching lines @@
     List<List<List<String>>> aCollection = [];
     List<List<String>> strArrArr;
     for (strArrArr in aCollection) {}
   }
 
 }
 
 main() {
   ForInTest.testMain();
 }