Change the pacing sender to always pacing the initial burst, even when

net/quic/congestion_control/pacing_sender.cc

Index: net/quic/congestion_control/pacing_sender.cc
diff --git a/net/quic/congestion_control/pacing_sender.cc b/net/quic/congestion_control/pacing_sender.cc
index 20d2b3b819a14f48b09b9ba80e32a3a62b950ffb..03e553477ced4ea1e0f08ae81e63e838d8bf3f0d 100644
--- a/net/quic/congestion_control/pacing_sender.cc
+++ b/net/quic/congestion_control/pacing_sender.cc
@@ -15,15 +15,12 @@ PacingSender::PacingSender(SendAlgorithmInterface* sender,
       burst_tokens_(initial_packet_burst),
       last_delayed_packet_sent_time_(QuicTime::Zero()),
       next_packet_send_time_(QuicTime::Zero()),
-      was_last_send_delayed_(false),
-      has_valid_rtt_(false) {
+      was_last_send_delayed_(false) {
 }
 
 PacingSender::~PacingSender() {}
 
 void PacingSender::SetFromConfig(const QuicConfig& config, bool is_server) {
-  // TODO(ianswett): Consider using the suggested RTT for pacing an initial
-  // response.
   sender_->SetFromConfig(config, is_server);
 }
 
@@ -42,9 +39,6 @@ void PacingSender::OnCongestionEvent(bool rtt_updated,
                                      QuicByteCount bytes_in_flight,
                                      const CongestionVector& acked_packets,
                                      const CongestionVector& lost_packets) {
-  if (rtt_updated) {
-    has_valid_rtt_ = true;
-  }
   sender_->OnCongestionEvent(
       rtt_updated, bytes_in_flight, acked_packets, lost_packets);
 }
@@ -55,11 +49,10 @@ bool PacingSender::OnPacketSent(
     QuicPacketSequenceNumber sequence_number,
     QuicByteCount bytes,
     HasRetransmittableData has_retransmittable_data) {
-  // Only pace data packets once we have an updated RTT.
   const bool in_flight =
       sender_->OnPacketSent(sent_time, bytes_in_flight, sequence_number,
                             bytes, has_retransmittable_data);
-  if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA || !has_valid_rtt_) {
+  if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA) {
     return in_flight;
   }
   if (burst_tokens_ > 0) {
@@ -117,10 +110,6 @@ QuicTime::Delta PacingSender::TimeUntilSend(
       HasRetransmittableData has_retransmittable_data) const {
   QuicTime::Delta time_until_send =
       sender_->TimeUntilSend(now, bytes_in_flight, has_retransmittable_data);
-  if (!has_valid_rtt_) {
-    // Don't pace if we don't have an updated RTT estimate.
-    return time_until_send;
-  }
   if (bytes_in_flight == 0) {
     // Add more burst tokens anytime the connection is entering quiescence.
     burst_tokens_ = initial_packet_burst_;
@@ -143,6 +132,8 @@ QuicTime::Delta PacingSender::TimeUntilSend(
   }
 
   // If the next send time is within the alarm granularity, send immediately.
+  // TODO(ianswett): This granularity logic ends up sending more packets than
+  // intended in an effort to make up for lost time that wasn't lost.
   if (next_packet_send_time_ > now.Add(alarm_granularity_)) {
     DVLOG(1) << "Delaying packet: "
              << next_packet_send_time_.Subtract(now).ToMicroseconds();