fixes css tests, now they can also run in browsers too.

utils/tests/css/src/ExpressionTest.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("ExpressionTest");
 #import("../../../css/css.dart");
 
 class ExpressionTest {
 
   static testMain() {
     initCssWorld();
 
     testClass();
     testId();
     testElement();
@@ skipping 508 matching lines @@
   static void testNegation() {
     // TODO(terry): Implement
   }
 
 }
 
 
 main() {
   ExpressionTest.testMain();
 }