Add CSS as a source file type.

tests/presubmit_unittest.py

 #!/usr/bin/env python
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for presubmit_support.py and presubmit_canned_checks.py."""
 
 # pylint: disable=E1101,E1103
 
 import logging
@@ skipping 1049 matching lines @@
         ],
         [
           # Expected.
         ],
       ),
     ]
     input_api = presubmit.InputApi(
         self.fake_change, './PRESUBMIT.py', False, None, False)
     self.mox.ReplayAll()
 
-    self.assertEqual(len(input_api.DEFAULT_WHITE_LIST), 21)
+    self.assertEqual(len(input_api.DEFAULT_WHITE_LIST), 22)
     self.assertEqual(len(input_api.DEFAULT_BLACK_LIST), 11)
     for item in files:
       results = filter(input_api.FilterSourceFile, item[0])
       for i in range(len(results)):
         self.assertEquals(results[i].LocalPath(),
                           presubmit.normpath(item[1][i]))
       # Same number of expected results.
       self.assertEquals(sorted([f.LocalPath().replace(presubmit.os.sep, '/')
                                 for f in results]),
                         sorted(item[1]))
@@ skipping 1202 matching lines @@
         owners_check=True)
     self.assertEqual(1, len(results))
     self.assertEqual(
         'Found line ending with white spaces in:', results[0]._message)
     self.checkstdout('')
 
 
 if __name__ == '__main__':
   import unittest
   unittest.main()