Revert "Remove Expect from core library."

tests/language/list_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.
 // Test program for array literals.
 
-import "package:expect/expect.dart";
-
 class ListLiteralTest {
 
   static const LAUREL = 1;
   static const HARDY  = 2;
 
   static testMain() {
 
     var funny = <int>[LAUREL, HARDY, ];  // Check that trailing comma works.
     Expect.equals(2, funny.length);
 
@@ skipping 26 matching lines @@
     Expect.equals(1, e2[0]);
     Expect.equals(2.0, e2[1]);
     Expect.equals(3, e2[2]);
     Expect.equals(200000.0, e2[3]);
   }
 }
 
 main() {
   ListLiteralTest.testMain();
 }