protected Map<String, List<String>> params() {
    return Collections.unmodifiableMap(params);
  }
Sets the value for the HTTP header field name {@link HttpHeaders#X_GOOG_MAPS_EXPERIENCE_ID}.
Passing null to this method will unset the experienceId header field.

@param experienceIds The experience IDs
src/main/java/com/google/maps/PendingResultBase.java