def CheckChange(input_api, output_api):
  """Checks that changes to client_variations.proto are mirrored."""
  has_proto_update = False
  has_parser_update = False
  cwd = input_api.PresubmitLocalPath()
  for path in input_api.AbsoluteLocalPaths():
    if not path.startswith(cwd):
      continue
    name = input_api.os_path.relpath(path, cwd)
    if name == 'client_variations.proto':
      has_proto_update = True
    elif name == 'devtools/client_variations_parser.js':
      has_parser_update = True

  results = []
  if has_proto_update and not has_parser_update:
    results.append(output_api.PresubmitPromptWarning(
        'client_variations.proto was changed. Does the JS parser at '
        'devtools/client_variations_parser.js need to be updated as well?'))
  return results