Revert "Remove Expect from core library."

tests/language/map_literal3_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.
 // Test program for map literals.
 
-import "package:expect/expect.dart";
-
 class MapLiteralTest {
 
   static testMain() {
     var map = { "a": 1, "b": 2, "c": 3 };
 
     Expect.equals(map.length, 3);
     Expect.equals(map["a"], 1);
     Expect.equals(map["z"], null);
     Expect.equals(map["c"], 3);
 
@@ skipping 79 matching lines @@
     // Map literals at beginning of statement.
     <String, num>{"pink": 100};
     const <String, num>{"floyd": 100};
   }
 }
 
 
 main() {
   MapLiteralTest.testMain();
 }