const std::string& UserAgent() {
  static const std::string s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
  return s_user_agent;
}
const std::string& UserAgent() {
  static const std::string s_user_agent = std::string("Webcc/") + WEBCC_VERSION;
  return s_user_agent;
}