Land Recent QUIC changes.

net/quic/congestion_control/inter_arrival_sender.cc

Index: net/quic/congestion_control/inter_arrival_sender.cc
diff --git a/net/quic/congestion_control/inter_arrival_sender.cc b/net/quic/congestion_control/inter_arrival_sender.cc
index c8d2c86ae95773a2b0ec21a84d12a54b12f6f94f..07421ae2b0304aefccf7849b3d69196dfb47a1e0 100644
--- a/net/quic/congestion_control/inter_arrival_sender.cc
+++ b/net/quic/congestion_control/inter_arrival_sender.cc
@@ -14,6 +14,8 @@ const float kMaxBitrateReduction = 0.9f;
 const float kMinBitrateReduction = 0.05f;
 const uint64 kMinBitrateKbit = 10;
 const int kInitialRttMs = 60;  // At a typical RTT 60 ms.
+const float kAlpha = 0.125f;
+const float kOneMinusAlpha = 1 - kAlpha;
 
 static const int kBitrateSmoothingPeriodMs = 1000;
 static const int kMinBitrateSmoothingPeriodMs = 500;
@@ -200,18 +202,25 @@ void InterArrivalSender::OnIncomingAck(
     QuicPacketSequenceNumber /*acked_sequence_number*/,
     QuicByteCount acked_bytes,
     QuicTime::Delta rtt) {
-  DCHECK(!rtt.IsZero());
-  DCHECK(!rtt.IsInfinite());
+  // RTT can't be negative.
+  DCHECK_LE(0, rtt.ToMicroseconds());
+
+  if (probing_) {
+    probe_->OnAcknowledgedPacket(acked_bytes);
+  }
+
+  if (rtt.IsInfinite()) {
+    return;
+  }
+
   if (smoothed_rtt_.IsZero()) {
     smoothed_rtt_ = rtt;
   } else {
     smoothed_rtt_ = QuicTime::Delta::FromMicroseconds(
-        (smoothed_rtt_.ToMicroseconds() * 3 + rtt.ToMicroseconds()) / 4);
-  }
-  state_machine_->set_rtt(SmoothedRtt());
-  if (probing_) {
-    probe_->OnAcknowledgedPacket(acked_bytes);
+        kOneMinusAlpha * smoothed_rtt_.ToMicroseconds() +
+        kAlpha * rtt.ToMicroseconds());
   }
+  state_machine_->set_rtt(smoothed_rtt_);
 }
 
 void InterArrivalSender::OnIncomingLoss(QuicTime ack_receive_time) {
@@ -305,6 +314,12 @@ QuicTime::Delta InterArrivalSender::SmoothedRtt() {
   return smoothed_rtt_;
 }
 
+QuicTime::Delta InterArrivalSender::RetransmissionDelay() {
+  // TODO(pwestin): Calculate and return retransmission delay.
+  // Use 2 * the smoothed RTT for now.
+  return smoothed_rtt_.Add(smoothed_rtt_);
+}
+
 void InterArrivalSender::EstimateNewBandwidth(QuicTime feedback_receive_time,
                                               QuicBandwidth sent_bandwidth) {
   QuicBandwidth new_bandwidth = bitrate_ramp_up_->GetNewBitrate(sent_bandwidth);