gfe-relnote: Allow client to enable QUIC bbr2 congestion control on server. Protected by --gfe2_reloadable_flag_quic_allow_client_enabled_bbr_v2.

PiperOrigin-RevId: 258653066
Change-Id: I921df5333a16224f118b2d4d2e423d7e3f2deaf4
diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index e7cd1a5..5762333 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -174,6 +174,12 @@
   if (config.HasClientRequestedIndependentOption(kTBBR, perspective)) {
     SetSendAlgorithm(kBBR);
   }
+  if (GetQuicReloadableFlag(quic_allow_client_enabled_bbr_v2) &&
+      config.HasClientRequestedIndependentOption(kB2ON, perspective)) {
+    QUIC_RELOADABLE_FLAG_COUNT(quic_allow_client_enabled_bbr_v2);
+    SetSendAlgorithm(kBBRv2);
+  }
+
   if (config.HasClientRequestedIndependentOption(kRENO, perspective)) {
     SetSendAlgorithm(kRenoBytes);
   } else if (config.HasClientRequestedIndependentOption(kBYTE, perspective) ||
@@ -184,6 +190,7 @@
              config.HasClientRequestedIndependentOption(kTPCC, perspective)) {
     SetSendAlgorithm(kPCC);
   }
+
   // Initial window.
   if (GetQuicReloadableFlag(quic_unified_iw_options)) {
     if (config.HasClientRequestedIndependentOption(kIW03, perspective)) {