webkitpy: Make all regex strings use raw string literals.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/models/test_expectations.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 292 matching lines @@
                 if state != 'start':
                     warnings.append('"%s" is not at the start of the line.' % token)
                     break
                 if token.startswith(WEBKIT_BUG_PREFIX):
                     bugs.append(token)
                 elif token.startswith(CHROMIUM_BUG_PREFIX):
                     bugs.append(token)
                 elif token.startswith(V8_BUG_PREFIX):
                     bugs.append(token)
                 else:
-                    match = re.match('Bug\((\w+)\)$', token)
+                    match = re.match(r'Bug\((\w+)\)$', token)
                     if not match:
                         warnings.append('unrecognized bug identifier "%s"' % token)
                         break
                     else:
                         bugs.append(token)
             elif token == '[':
                 if state == 'start':
                     state = 'configuration'
                 elif state == 'name_found':
                     state = 'expectations'
@@ skipping 865 matching lines @@
             # If reconstitute_only_these is an empty list, we want to return original_string.
             # So we need to compare reconstitute_only_these to None, not just check if it's falsey.
             if reconstitute_only_these is None or expectation_line in reconstitute_only_these:
                 return expectation_line.to_string(test_configuration_converter)
             return expectation_line.original_string
 
         def nones_out(expectation_line):
             return expectation_line is not None
 
         return "\n".join(filter(nones_out, map(serialize, expectation_lines)))