Fix check_package_boundaries presubmit test for Windows.

tools-webrtc/check_package_boundaries.py

 #!/usr/bin/env python
 
 # Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
@@ skipping 36 matching lines @@
       else:
         self.messages_left -= 1
     message = ERROR_MESSAGE.format(build_file_path, line_number, target_name,
                                    source_file, subpackage)
     logging.log(self.log_level, message)
 
 
 def _BuildSubpackagesPattern(packages, query):
   """Returns a regular expression that matches source files inside subpackages
   of the given query."""
-  query += '/'
+  query += os.path.sep
   length = len(query)
   pattern = r'(?P<line_number>\d+)\$\s*"(?P<source_file>(?P<subpackage>'
-  pattern += '|'.join(package[length:] for package in packages
-                      if package.startswith(query))
+  pattern += '|'.join(package[length:].replace(os.path.sep, '/')
+                      for package in packages if package.startswith(query))
   pattern += r')/[\w\./]*)"'
   return re.compile(pattern)
 
 
 def _ReadFileAndPrependLines(file_path):
   """Reads the contents of a file and prepends the line number to every line."""
   with open(file_path) as f:
     return "".join("{}${}".format(line_number, line)
                    for line_number, line in enumerate(f, 1))
 
@@ skipping 56 matching lines @@
 
   logging.basicConfig(format=LOG_FORMAT)
   logging.getLogger().setLevel(DISPLAY_LEVEL)
   logger = Logger(args.max_messages)
 
   return CheckPackageBoundaries(args.root_dir, logger, args.build_files)
 
 
 if __name__ == '__main__':
   sys.exit(main())