Revert "Remove Expect from core library."

tests/language/map_literal_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 map literals.
 
 class MapLiteralTest {
   MapLiteralTest() {}
 
   static testMain() {
     var test = new MapLiteralTest();
     test.testStaticInit();
     test.testConstInit();
   }
@@ skipping 52 matching lines @@
     Expect.equals(2, map1["b"]);
 
     Expect.equals(1, map2["1"]);
     Expect.equals(2, map2["2"]);
   }
 }
 
 main() {
   MapLiteralTest.testMain();
 }