gfe-relnote: In QUIC, when cwnd gets bootstrapped, set cwnd gain in STARTUP to 2 to avoid too much overshooting. This only affects cwnd bootstrapping experiment.

PiperOrigin-RevId: 247584028
Change-Id: I36d3588ffc91452d235648405a6feda8009db476

quic/core/congestion_control/bbr_sender.cc

diff --git a/quic/core/congestion_control/bbr_sender.cc b/quic/core/congestion_control/bbr_sender.cc
index 2c0ad34..004ec91 100644
--- a/quic/core/congestion_control/bbr_sender.cc
+++ b/quic/core/congestion_control/bbr_sender.cc
@@ -355,6 +355,8 @@
     if (new_cwnd > congestion_window_) {
       QUIC_RELOADABLE_FLAG_COUNT_N(quic_fix_bbr_cwnd_in_bandwidth_resumption, 1,
                                    2);
+      // Decrease cwnd gain when cwnd increases.
+      set_high_cwnd_gain(kDerivedHighCWNDGain);
     } else {
       QUIC_RELOADABLE_FLAG_COUNT_N(quic_fix_bbr_cwnd_in_bandwidth_resumption, 2,
                                    2);