t functionName() {
      return this.functionName_;
    }

    get measureName() {
      return this.measureName_;
    }

    get startMark() {
      return this.startMark_ || tr.b.getOnlyElement(
          window.performance.getEntriesByName(this.startMarkName_));
    }

    get endMark() {
      return this.endMark_ || tr.b.getOnlyElement(
          window.performance.getEntriesByName(this.endMarkName_));
    }

    get durationMs() {
      // There may be many measures named `this.measureName`, but the s