message: [XLA] Don't call timer->Nanoseconds() on a not-ok stream.
  If the stream is not OK, the timer might not have been initialized and
  finalized, in which case calling timer->Nanoseconds() is illegal and
  will crash.
diff: @@ -230,7 +230,11 @@ StatusOr<ReturnT> Executable::ExecuteOnStreamWrapper(
  profile->MergeFrom(execution_profile());
  // Overall execution time (in nanoseconds) from the executor timer.
  + if (stream->ok()) {
  + // Don't read timer->Nanoseconds() if the stream isn't OK -- that's
  + // illegal.
  profile->set_compute_and_transfer_time_ns(timer->Nanoseconds());
  + }
  // TODO(b/28123297): On GPU we end up including transfer time in
  // the compute time this way. Instead, we should get the correct
  