def _IsValidPrimaryOwnerEmail(owner_tag_text):
  """Returns true if |owner_tag_text| is a valid primary owner.

  A valid primary owner is an individual (not a team) with a Chromium or Google
  email address.

  Args:
    owner_tag_text: The text in an owner tag
  """
  if '-' in owner_tag_text:  # Check whether it's a team email address.
    return False

  return (owner_tag_text.endswith('@chromium.org')
          or owner_tag_text.endswith('@google.com'))