code: function(sampleIndices) {
        sampleIndices.sort();
  
        var ret = [];
        this.series_.forEach(function(series) {
          ret.push(series.getStatistics(sampleIndices));
        });
        return ret;
      }
docs: Obtains min, max, avg, values, start, and end for different series for
  a given counter
  getSampleStatistics([0,1])
  The statistics objects that this returns are an array of objects, one
  object for each series for the counter in the form:
  {min: minVal, max: maxVal, avg: avgVal, start: startVal, end: endVal}
  
  @param {Array.<Number>} Indices to summarize.
  @return {Object} An array of statistics. Each element in the array
  has data for one of the series in the selected counter.