/**
  * Get the Sum of all the stats that are watched, for all the stats added with add() since the
  * last call to clear() in JSON.
  *
  * @return The Sum of all the stats since last clear() in JSON.
  */
 public String getSumJSON() {
   String str =
       String.format(
           FakeUserStats.jsonMediaStreamStatsTemplate,
           -1, // ssrc not needed here
           downloadJitterMs.getSum(),
           downloadPercentLoss.getSum(),
           downloadRateKiloBitPerSec.getSum(),
           jitterBufferDelayMs.getSum(),
           jitterBufferDelayPackets.getSum(),
           nbDiscarded.getSum(),
           nbDiscardedFull.getSum(),
           nbDiscardedLate.getSum(),
           nbDiscardedReset.getSum(),
           nbDiscardedShrink.getSum(),
           nbFec.getSum(),
           nbPackets.getSum(),
           nbPacketsLost.getSum(),
           nbReceivedBytes.getSum(),
           nbSentBytes.getSum(),
           packetQueueCountPackets.getSum(),
           packetQueueSize.getSum(),
           percentDiscarded.getSum(),
           rttMs.getSum(),
           uploadJitterMs.getSum(),
           uploadPercentLoss.getSum(),
           uploadRateKiloBitPerSec.getSum());
   return str;
 }