Add more information to LOG(DFATAL) in QUIC's tcp_loss_algorithm.

net/quic/congestion_control/tcp_loss_algorithm.cc

Index: net/quic/congestion_control/tcp_loss_algorithm.cc
diff --git a/net/quic/congestion_control/tcp_loss_algorithm.cc b/net/quic/congestion_control/tcp_loss_algorithm.cc
index 557681ee1864932a3da015054e208e03a97a259f..b0a5a15b4972fa0baacaf34e3638c9fab3502587 100644
--- a/net/quic/congestion_control/tcp_loss_algorithm.cc
+++ b/net/quic/congestion_control/tcp_loss_algorithm.cc
@@ -46,7 +46,9 @@ SequenceNumberSet TCPLossAlgorithm::DetectLostPackets(
     }
 
     LOG_IF(DFATAL, it->nack_count == 0)
-        << "All packets less than largest observed should have been nacked.";
+        << "All packets less than largest observed should have been nacked."
+        << "sequence_number:" << sequence_number
+        << " largest_observed:" << largest_observed;
     if (it->nack_count >= kNumberOfNacksBeforeRetransmission) {
       lost_packets.insert(sequence_number);
       continue;