function PerfMeasurement(id, name, reent) {
        this.name = name;
        this.reent = reent;
        if (id) {
            this.id = id;
        } else {
            this.id = (reent) ? "[reent " + this.reent + "] " + name : name;
        }
    }
@private
A unique key to log performance data

@param {(string|undefined)} id Unique ID for this measurement name
@param {!string} name A short name for this measurement
@param {?number} reent Sequence identifier for parallel tests of the same name