Use byte conservation instead of packet conservation in QUIC's Slow Start Large Recovery experiment…

net/quic/congestion_control/tcp_cubic_sender_bytes.cc

Index: net/quic/congestion_control/tcp_cubic_sender_bytes.cc
diff --git a/net/quic/congestion_control/tcp_cubic_sender_bytes.cc b/net/quic/congestion_control/tcp_cubic_sender_bytes.cc
index 398048782718d63d3193d67b515ba5f7717428d1..863def3b366bd2b7bbf3576ef47e94fe1914c74c 100644
--- a/net/quic/congestion_control/tcp_cubic_sender_bytes.cc
+++ b/net/quic/congestion_control/tcp_cubic_sender_bytes.cc
@@ -81,16 +81,18 @@ void TcpCubicSenderBytes::ExitSlowstart() {
 }
 
 void TcpCubicSenderBytes::OnPacketLost(QuicPacketNumber packet_number,
+                                       QuicByteCount lost_bytes,
                                        QuicByteCount bytes_in_flight) {
   // TCP NewReno (RFC6582) says that once a loss occurs, any losses in packets
   // already sent should be treated as a single loss event, since it's expected.
   if (packet_number <= largest_sent_at_last_cutback_) {
     if (last_cutback_exited_slowstart_) {
       ++stats_->slowstart_packets_lost;
+      stats_->slowstart_bytes_lost += lost_bytes;
       if (slow_start_large_reduction_) {
-        // Reduce congestion window by 1 MSS for every loss.
+        // Reduce congestion window by lost_bytes for every loss.
         congestion_window_ =
-            max(congestion_window_ - kDefaultTCPMSS, min_congestion_window_);
+            max(congestion_window_ - lost_bytes, min_congestion_window_);
         slowstart_threshold_ = congestion_window_;
       }
     }