Expose packet loss counts from QUIC to NetworkQualityEstimator

net/quic/quic_connection_logger.cc

Index: net/quic/quic_connection_logger.cc
diff --git a/net/quic/quic_connection_logger.cc b/net/quic/quic_connection_logger.cc
index fe529d882b21d32425f8c6cd7d0e327d0fb9b9dd..0ceed7fddc3d3d9a7df940dcb0390447cf46782c 100644
--- a/net/quic/quic_connection_logger.cc
+++ b/net/quic/quic_connection_logger.cc
@@ -500,6 +500,9 @@ void QuicConnectionLogger::OnProtocolVersionMismatch(
 void QuicConnectionLogger::OnPacketHeader(const QuicPacketHeader& header) {
   net_log_.AddEvent(NetLog::TYPE_QUIC_SESSION_PACKET_AUTHENTICATED);
   ++num_packets_received_;
+
+  const QuicPacketCount previous_largest_received_packet_number =
+      largest_received_packet_number_;
   if (largest_received_packet_number_ < header.packet_number) {
     QuicPacketNumber delta =
         header.packet_number - largest_received_packet_number_;
@@ -525,6 +528,44 @@ void QuicConnectionLogger::OnPacketHeader(const QuicPacketHeader& header) {
                                                  header.packet_number));
   }
   last_received_packet_number_ = header.packet_number;
+  ReportIncrementalPacketCounts(previous_largest_received_packet_number);
+}
+
+void QuicConnectionLogger::ReportIncrementalPacketCounts(
+    QuicPacketCount previous_largest_received_packet_number) const {
+  DCHECK_GE(largest_received_packet_number_,
+            previous_largest_received_packet_number);
+  if (!socket_performance_watcher_)
+    return;
+
+  size_t packets_missing = 0;
+  size_t packets_received_in_order = 0;
+  size_t packets_received_out_of_order = 0;
+
+  const size_t diff =
+      largest_received_packet_number_ - previous_largest_received_packet_number;
+
+  if (diff == 0) {
+    // The received packet number has a lower sequence number than the expected
+    // sequence number.
+    packets_received_out_of_order = 1;
+  } else if (diff == 1) {
+    // The received packet number has the same sequence number as the expected
+    // sequence number.
+    packets_received_in_order = 1;
+  } else {
+    // The received packet number has higher sequence number as the expected
+    // sequence number. Report all packets with intermediate sequence numbers
+    // as newly missing, but they may be received later and will be counted as
+    // out of order.
+    // TODO(tbansal): Do not report if |diff| is more than a threshold to avoid
+    // cases where the QUIC transmitter skips certain packet sequence numbers.
+    packets_missing = diff - 1;
+    packets_received_in_order = 1;
+  }
+  socket_performance_watcher_->OnIncrementalPacketCountAvailable(
+      packets_missing, packets_received_in_order,
+      packets_received_out_of_order);
 }
 
 void QuicConnectionLogger::OnStreamFrame(const QuicStreamFrame& frame) {
@@ -772,8 +813,8 @@ void QuicConnectionLogger::AddTo21CumulativeHistogram(
 float QuicConnectionLogger::ReceivedPacketLossRate() const {
   if (largest_received_packet_number_ <= num_packets_received_)
     return 0.0f;
-  float num_received = largest_received_packet_number_ - num_packets_received_;
-  return num_received / largest_received_packet_number_;
+  float num_lost = largest_received_packet_number_ - num_packets_received_;
+  return num_lost / largest_received_packet_number_;
 }
 
 void QuicConnectionLogger::OnRttChanged(QuicTime::Delta rtt) const {