}

  // Adds synchronization events to 'stream' that wait for this tensor to be
  // defined on 'stream'. Does nothing if the tensor is already defined on that
  // stream.
  void WaitForDefinitionEventOnStream(se::Stream* stream);

  // (Re)sets the definition event of the tensor to 'event', and promises that
  // the tensor has already been defined on stream. Removes any previous

    index_to_buffer.second = buffer.Release();
  }

  VLOG(4) << shaped_buffer.ToString();

  set_shaped_buffer(std::move(shaped_buffer));
  return absl::OkStatus();
}

void XlaTensor::WaitForDefinitionEventOnStream(se::Stream* stream) {
  mutex_lock lock(mu_);
  if (!definition_event_) {
    return;
  }

  // The set of defined streams is expected to be very small indeed (usually