Fix all "dangerous-default-value" pylint warnings.

third_party/WebKit/Tools/Scripts/webkitpy/style/optparser_unittest.py

 # Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
 #     documentation and/or other materials provided with the distribution.
@@ skipping 22 matching lines @@
 
 class ArgumentPrinterTest(unittest.TestCase):
 
     """Tests the ArgumentPrinter class."""
 
     _printer = ArgumentPrinter()
 
     def _create_options(self,
                         output_format='emacs',
                         min_confidence=3,
-                        filter_rules=[],
+                        filter_rules=None,
                         git_commit=None):
         return ProcessorOptions(filter_rules=filter_rules,
                                 git_commit=git_commit,
                                 min_confidence=min_confidence,
                                 output_format=output_format)
 
     def test_to_flag_string(self):
         options = self._create_options('vs7', 5, ['+foo', '-bar'], 'git')
         self.assertEqual('--filter=+foo,-bar --git-commit=git '
                          '--min-confidence=5 --output=vs7',
@@ skipping 193 matching lines @@
         self.assertFalse(options.__eq__(ProcessorOptions(is_verbose=True)))
         self.assertFalse(options.__eq__(ProcessorOptions(min_confidence=2)))
         self.assertFalse(options.__eq__(ProcessorOptions(output_format="vs7")))
 
     def test_ne(self):
         """Test __ne__ inequality function."""
         # By default, __ne__ always returns true on different objects.
         # Thus, just check the distinguishing case to verify that the
         # code defines __ne__.
         self.assertFalse(ProcessorOptions().__ne__(ProcessorOptions()))