unittest step2: bye bye to multiple entrypoints for unittest

client/tests/client/dom/WindowManglingTest.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.
 
 #library('WindowManglingTest');
-#import('../../../../lib/unittest/unittest_dom.dart');
+#import('../../../../lib/unittest/unittest.dart');
+#import('../../../../lib/unittest/dom_config.dart');
 #import('dart:dom', prefix: 'dom');
 
 // Defined in dom.Window.
 get navigator() => "Dummy";
 
 $eq(x, y) => false;
 $eq$(x, y) => false;
 
 main() {
+  useDomConfiguration();
   var win = dom.window;
 
   test('windowMethod', () {
       final message = navigator;
       final x = win.navigator;
       Expect.notEquals(message, x);
     });
 
   test('windowEquals', () {
       Expect.isFalse($eq(win, win));
       Expect.isTrue(win == win);
     });
 
   test('windowEquals', () {
       Expect.isFalse($eq$(win, win));
       Expect.isTrue(win == win);
     });
 }