Add a new rate based sending connection option which uses the pacing rate to keep the bytes_in_flig…

net/quic/congestion_control/tcp_cubic_sender_base.h

Index: net/quic/congestion_control/tcp_cubic_sender_base.h
diff --git a/net/quic/congestion_control/tcp_cubic_sender_base.h b/net/quic/congestion_control/tcp_cubic_sender_base.h
index a550bbbb90dc35d2bae44a726c83fb50712e5cf3..55ac920f2892d3dae559393d062bcf10810937d8 100644
--- a/net/quic/congestion_control/tcp_cubic_sender_base.h
+++ b/net/quic/congestion_control/tcp_cubic_sender_base.h
@@ -61,7 +61,7 @@ class NET_EXPORT_PRIVATE TcpCubicSenderBase : public SendAlgorithmInterface {
   void OnConnectionMigration() override;
   QuicTime::Delta TimeUntilSend(QuicTime now,
                                 QuicByteCount bytes_in_flight) const override;
-  QuicBandwidth PacingRate() const override;
+  QuicBandwidth PacingRate(QuicByteCount bytes_in_flight) const override;
   QuicBandwidth BandwidthEstimate() const override;
   QuicTime::Delta RetransmissionDelay() const override;
   bool InSlowStart() const override;
@@ -143,6 +143,9 @@ class NET_EXPORT_PRIVATE TcpCubicSenderBase : public SendAlgorithmInterface {
   // When true, exit slow start with large cutback of congestion window.
   bool slow_start_large_reduction_;
 
+  // When true, use rate based sending instead of only sending if there's CWND.
+  bool rate_based_sending_;
+
   // When true, use unity pacing instead of PRR.
   bool no_prr_;