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.
  
  """Create files with copyright boilerplate and header include guards.
  
  Usage: tools/boilerplate.py path/to/file.{h,cc}
  """
  
  from datetime import date
  import os
  import os.path
  import sys
  
  LINES = [
      'Copyright %d The Chromium Authors. All rights reserved.' %
          date.today().year,
      'Use of this source code is governed by a BSD-style license that can be',
      'found in the LICENSE file.'
  ]
  
  EXTENSIONS_TO_COMMENTS = {
      'h': '//',
      'cc': '//',
      'mm': '//',
      'js': '//',
      'py': '#'
  }
  
  def _GetHeader(filename):
    _, ext = os.path.splitext(filename)
    ext = ext[1:]
    comment = EXTENSIONS_TO_COMMENTS[ext] + ' '
    return '\n'.join([comment + line for line in LINES])
  
  
  def _CppHeader(filename):
    guard = filename.replace('/', '_').replace('.', '_').upper() + '_'
    return '\n'.join([
      '',
      '#ifndef ' + guard,
      '#define ' + guard,
      '',
      '#endif  // ' + guard,
      ''
    ])
  
  
  def _CppImplementation(filename):
    base, _ = os.path.splitext(filename)
    include = '#include "' + base + '.h"'
    return '\n'.join(['', include])
  
  
  def _CreateFile(filename):
    contents = _GetHeader(filename) + '\n'
  
    if filename.endswith('.h'):
      contents += _CppHeader(filename)
    elif filename.endswith('.cc') or filename.endswith('.mm'):
      contents += _CppImplementation(filename)
  
    fd = open(filename, 'w')
    fd.write(contents)
    fd.close()
  
  
  def Main():
    files = sys.argv[1:]
    if len(files) < 1:
      print >> sys.stderr, 'Usage: boilerplate.py path/to/file.h path/to/file.cc'
      return 1
  
    # Perform checks first so that the entire operation is atomic.
    for f in files:
      _, ext = os.path.splitext(f)
      if not ext[1:] in EXTENSIONS_TO_COMMENTS:
        print >> sys.stderr, 'Unknown file type for %s' % f
        return 2
  
      if os.path.exists(f):
        print >> sys.stderr, 'A file at path %s already exists' % f
        return 2
  
    for f in files:
      _CreateFile(f)
  
  
  if __name__ == '__main__':
    sys.exit(Main())
  
subject: Add tools/boilerplate.py that will generate files with copyright headers and guards.