Remove Expect from core library.

tests/corelib/map_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.
 
 library map_test;
+import "package:expect/expect.dart";
 import 'dart:collection';
 
 class MapTest {
 
   static testMain() {
     test(new HashMap());
     test(new LinkedHashMap());
     test(new SplayTreeMap());
     testLinkedHashMap();
     testMapLiteral();
@@ skipping 225 matching lines @@
     m.remove("a");
     Expect.equals(2, m.length);
     Expect.equals(null, m["a"]);
     Expect.equals(false, m.containsKey("a"));
   }
 }
 
 main() {
   MapTest.testMain();
 }