Removed obsolete code

utils/css/cssworld.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.
-
-class CssWorld {
-  List<String> classes;
-  List<String> ids;
-
-  CssWorld(this.classes, this.ids) {
-    // Insure no private class names in our CSS world (._foo).
-    for (final aClass in classes) {
-      if (aClass.startsWith('_')) {
-        throw new CssSelectorException(
-            "private class ('_' prefix) not valid for CssWorld $aClass)");
-      }
-    }
-
-    // Insure no private element ids in our CSS world (#_foo).
-    for (final id in ids) {
-      if (id.startsWith('_')) {
-        throw new CssSelectorException(
-            "private id ('_' prefix) not valid for CssWorld $id)");
-      }
-    }
-  }
-}