/**
  * Sets the user agent to use for this emulation profile. While {@link
  * com.opera.core.systems.EmulationProfile#getUserAgent()} returns a string, {@link
  * OperaMobileEmulation.UserAgent} provides a convenience enum of the supported user agent
  * strings in Opera Mobile.
  *
  * @param userAgent the user agent to use
  * @return self-reference
  */
 public Builder setUserAgent(UserAgent userAgent) {
   config.userAgent = userAgent;
   return this;
 }