e;

    this.startStackFrame = undefined;
    this.endStackFrame = undefined;

    this.duration = duration;

    // isTopLevel is set at import because only NESTABLE_ASYNC events might not
    // be topLevel. All legacy async events are toplevel by definition.
    this.isTopLevel = (opt_isTopLevel === true);

    if (opt_cpuStart !== undefined) {
      this.cpuStart = opt_cpuStart;
    }

    if (opt_cpuDuration !== undefined) {
      this.cpuDuration = opt_cpuDuration;
    }

    if (opt_argsStripped !== 