xp.end),
          name: histogramName,
          description: 'RAIL stage ' + histogramName,
          perSecond: true
        };
      }
    }
  }

  /**
   * Gets a list of time intervals for the RAIL stages. Each RAIL stage
   * generates a time interval with the name equal to the name of the RAIL
   * stage except made into lower case and with spaces replaced bu underscores
   * e.g. "Scroll Animation" --> "scroll_animation". Each time interval is given
   * in the following form:
   *
   *   {
   *   