Update from https://crrev.com/312398

net/quic/quic_config.cc

Index: net/quic/quic_config.cc
diff --git a/net/quic/quic_config.cc b/net/quic/quic_config.cc
index e83b8b84cc45a59be9b432a2e13e41950a482af6..9d0a7c9bb3553c374fbc0e8a7620c534db2c0e2c 100644
--- a/net/quic/quic_config.cc
+++ b/net/quic/quic_config.cc
@@ -428,7 +428,7 @@ QuicConfig::QuicConfig()
     : max_time_before_crypto_handshake_(QuicTime::Delta::Zero()),
       max_idle_time_before_crypto_handshake_(QuicTime::Delta::Zero()),
       max_undecryptable_packets_(0),
-      congestion_feedback_(kCGST, PRESENCE_REQUIRED),
+      congestion_feedback_(kCGST, PRESENCE_OPTIONAL),
       connection_options_(kCOPT, PRESENCE_OPTIONAL),
       idle_connection_state_lifetime_seconds_(kICSL, PRESENCE_REQUIRED),
       silent_close_(kSCLS, PRESENCE_OPTIONAL),
@@ -443,16 +443,6 @@ QuicConfig::QuicConfig()
 
 QuicConfig::~QuicConfig() {}
 
-void QuicConfig::SetCongestionFeedback(
-    const QuicTagVector& congestion_feedback,
-    QuicTag default_congestion_feedback) {
-  congestion_feedback_.set(congestion_feedback, default_congestion_feedback);
-}
-
-QuicTag QuicConfig::CongestionFeedback() const {
-  return congestion_feedback_.GetTag();
-}
-
 void QuicConfig::SetConnectionOptionsToSend(
     const QuicTagVector& connection_options) {
   connection_options_.SetSendValues(connection_options);
@@ -611,6 +601,10 @@ bool QuicConfig::negotiated() const {
 
 void QuicConfig::SetDefaults() {
   QuicTagVector congestion_feedback;
+  // TODO(alyssar) stop sending this once QUIC_VERSION_23 is sunset.
+  // This field was required until version 22 was removed but by the time
+  // QUIC_VERSION_23 is sunset, no users of QUIC_VERSION_24 should be expecting
+  // it.
   congestion_feedback.push_back(kQBIC);
   congestion_feedback_.set(congestion_feedback, kQBIC);
   idle_connection_state_lifetime_seconds_.set(kMaximumIdleTimeoutSecs,