new_contents: #!/usr/bin/env python
  # Copyright 2014 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.
  
  import os
  import sys
  
  
  def RemoveAllStalePycFiles(base_dir):
    """Scan directories for old .pyc files without a .py file and delete them."""
    for dirname, _, filenames in os.walk(base_dir):
      if '.svn' in dirname or '.git' in dirname:
        continue
      for filename in filenames:
        root, ext = os.path.splitext(filename)
        if ext != '.pyc':
          continue
  
        pyc_path = os.path.join(dirname, filename)
        py_path = os.path.join(dirname, root + '.py')
  
        try:
          if not os.path.exists(py_path):
            os.remove(pyc_path)
        except OSError:
          # Wrap OS calls in try/except in case another process touched this file.
          pass
  
      try:
        os.removedirs(dirname)
      except OSError:
        # Wrap OS calls in try/except in case another process touched this dir.
        pass
  
  
  if __name__ == '__main__':
    for path in sys.argv[1:]:
      RemoveAllStalePycFiles(path)
  
subject: add tools/remove_stale_pyc_files.py