message: minor fix for step events converter.
diff: @@ -53,7 +53,7 @@ StepEvents ConvertHostThreadsXLineToStepEvents(
  int64 correlation_id = -1;
  int64 group_id = -1;
  event.ForEachStat([&](const XStatVisitor& stat) {
  - if (stat.Id() == StatType::kCorrelationId) {
  + if (stat.Type() == StatType::kCorrelationId) {
  correlation_id = stat.IntValue();
  } else if (stat.Type() == StatType::kGroupId) {
  group_id = stat.IntValue();
  