Add more detailed logging to QUIC's ack validation. No functional change.

net/quic/quic_connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 
 #include <algorithm>
@@ skipping 749 matching lines @@
     LOG(WARNING) << ENDPOINT << "Peer's observed unsent packet:"
                  << incoming_ack.largest_observed << " vs "
                  << packet_generator_.packet_number();
     // We got an error for data we have not sent.  Error out.
     return "Largest observed too high";
   }
 
   if (incoming_ack.largest_observed < sent_packet_manager_.largest_observed()) {
     LOG(WARNING) << ENDPOINT << "Peer's largest_observed packet decreased:"
                  << incoming_ack.largest_observed << " vs "
-                 << sent_packet_manager_.largest_observed();
+                 << sent_packet_manager_.largest_observed()
+                 << " packet_number:" << last_header_.packet_number
+                 << " largest seen with ack:" << largest_seen_packet_with_ack_
+                 << " connection_id: " << connection_id_;
     // A new ack has a diminished largest_observed value.  Error out.
     // If this was an old packet, we wouldn't even have checked.
     return "Largest observed too low";
   }
 
   if (!incoming_ack.missing_packets.Empty() &&
       incoming_ack.missing_packets.Max() > incoming_ack.largest_observed) {
     LOG(WARNING) << ENDPOINT << "Peer sent missing packet: "
                  << incoming_ack.missing_packets.Max()
                  << " which is greater than largest observed: "
@@ skipping 1563 matching lines @@
 }
 
 StringPiece QuicConnection::GetCurrentPacket() {
   if (current_packet_data_ == nullptr) {
     return StringPiece();
   }
   return StringPiece(current_packet_data_, last_size_);
 }
 
 }  // namespace net