code: function addMeasurement(id) {
          if (!enabled) {
              return;
          }
  
          if (!(id instanceof PerfMeasurement)) {
              id = new PerfMeasurement(id, id);
          }
  
          var elapsedTime = brackets.app.getElapsedMilliseconds();
  
          if (activeTests[id.id]) {
              elapsedTime -= activeTests[id.id].startTime;
              delete activeTests[id.id];
          }
  
          if (perfData[id]) {
              // We have existing data, add to it
              if (Array.isArray(perfData[id])) {
                  perfData[id].push(elapsedTime);
              } else {
                  // Current data is a number, convert to Array
                  perfData[id] = [perfData[id], elapsedTime];
              }
          } else {
              perfData[id] = elapsedTime;
          }
  
          if (id.reent !== undefined) {
              if (_reentTests[id] === 0) {
                  delete _reentTests[id];
              } else {
                  _reentTests[id]--;
              }
          }
  
      }
docs: Stop a timer and add its measurements to the performance data.
  
  Multiple measurements can be stored for any given name. If there are
  multiple values for a name, they are stored in an Array.
  
  If markStart() was not called for the specified timer, the
  measured time is relative to app startup.
  
  @param {Object} id  Timer id.