code: 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;
          }
      }
docs: @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