Change QUIC's pacing sender to send at 1.25x the estimated bandwidth

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 e84d1f2b01d866acaae5a59798d81f8c253467cf..f0f0e5dd092e19d4c4213585a9861055b936ddbd 100644
--- a/net/quic/congestion_control/pacing_sender.cc
+++ b/net/quic/congestion_control/pacing_sender.cc
@@ -67,9 +67,9 @@ bool PacingSender::OnPacketSent(
   }
   // The next packet should be sent as soon as the current packets has
   // been transferred.  We pace at twice the rate of the underlying
-  // sender's bandwidth estimate to help ensure that pacing doesn't become
-  // a bottleneck.
-  const float kPacingAggression = 2;
+  // sender's bandwidth estimate during slow start and 1.25x during congestion
+  // avoidance to ensure pacing doesn't prevent us from filling the window.
+  const float kPacingAggression = sender_->InSlowStart() ? 2 : 1.25;
   QuicTime::Delta delay =
       BandwidthEstimate().Scale(kPacingAggression).TransferTime(bytes);
   // If the last send was delayed, and the alarm took a long time to get
@@ -166,6 +166,10 @@ QuicByteCount PacingSender::GetCongestionWindow() const {
   return sender_->GetCongestionWindow();
 }
 
+bool PacingSender::InSlowStart() const {
+  return sender_->InSlowStart();
+}
+
 QuicByteCount PacingSender::GetSlowStartThreshold() const {
   return sender_->GetSlowStartThreshold();
 }