message: [tf.data] Reduce verbosity of a possibly spurious warning.
diff: @@ -210,7 +210,7 @@ class Node {
  processing_time_ += time_nanos - iter->second;
  work_start_.erase(iter);
  } else {
  - LOG(WARNING)
  + VLOG(1)
  << "Encountered a stop event that was not preceded by a start event.";
  }
  }
  