docs: function Snapshots(names, numSnapshots) {
    this.names = names || [];
    this.current = 0;
    this.counters = [];
    this.counters.length = numSnapshots || 0;
  
    var i, j;
    for (i=0; i<this.counters.length; i++) {
      this.counters[i] = {};
      for (j=0; j<this.names.length; j++) {
        this.counters[i][this.names[j]] = [0, 0];
      }
    }
  }