message: Add vlogging for compression data size.
diff: @@ -72,6 +72,8 @@ Status CompressElement(const std::vector<Tensor>& element,
  out->mutable_data())) {
  return errors::Internal("Failed to compress using snappy.");
  }
  + VLOG(3) << "Compressed element from " << total_size << " bytes to "
  + << out->data().size() << " bytes";
  return Status::OK();
  }
  