Deprecate FLAGS_quic_remove_obsolete_forward_secure.

net/quic/core/quic_connection.cc

Index: net/quic/core/quic_connection.cc
diff --git a/net/quic/core/quic_connection.cc b/net/quic/core/quic_connection.cc
index b52db56080b5039bd8d3a96e74b8d12042ddda6f..3d4a4e14b06e06f6642682798289bf11883032f0 100644
--- a/net/quic/core/quic_connection.cc
+++ b/net/quic/core/quic_connection.cc
@@ -199,8 +199,6 @@ QuicConnection::QuicConnection(QuicConnectionId connection_id,
       writer_(writer),
       owns_writer_(owns_writer),
       encryption_level_(ENCRYPTION_NONE),
-      has_forward_secure_encrypter_(false),
-      first_required_forward_secure_packet_(0),
       clock_(helper->GetClock()),
       random_generator_(helper->GetRandomGenerator()),
       connection_id_(connection_id),
@@ -637,13 +635,6 @@ void QuicConnection::OnDecryptedPacket(EncryptionLevel level) {
   last_decrypted_packet_level_ = level;
   last_packet_decrypted_ = true;
 
-  // If this packet was foward-secure encrypted and the forward-secure encrypter
-  // is not being used, start using it.
-  if (encryption_level_ != ENCRYPTION_FORWARD_SECURE &&
-      has_forward_secure_encrypter_ && level == ENCRYPTION_FORWARD_SECURE) {
-    SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
-  }
-
   // Once the server receives a forward secure packet, the handshake is
   // confirmed.
   if (level == ENCRYPTION_FORWARD_SECURE &&
@@ -1901,15 +1892,6 @@ void QuicConnection::SendOrQueuePacket(SerializedPacket* packet) {
   }
 
   QuicUtils::ClearSerializedPacket(packet);
-  // If a forward-secure encrypter is available but is not being used and the
-  // next packet number is the first packet which requires
-  // forward security, start using the forward-secure encrypter.
-  if (!FLAGS_quic_remove_obsolete_forward_secure &&
-      encryption_level_ != ENCRYPTION_FORWARD_SECURE &&
-      has_forward_secure_encrypter_ &&
-      packet->packet_number >= first_required_forward_secure_packet_ - 1) {
-    SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
-  }
 }
 
 void QuicConnection::OnPingTimeout() {
@@ -1978,18 +1960,6 @@ void QuicConnection::OnRetransmissionTimeout() {
 void QuicConnection::SetEncrypter(EncryptionLevel level,
                                   QuicEncrypter* encrypter) {
   packet_generator_.SetEncrypter(level, encrypter);
-  if (!FLAGS_quic_remove_obsolete_forward_secure &&
-      level == ENCRYPTION_FORWARD_SECURE) {
-    has_forward_secure_encrypter_ = true;
-    first_required_forward_secure_packet_ =
-        packet_number_of_last_sent_packet_ +
-        // 3 times the current congestion window (in slow start) should cover
-        // about two full round trips worth of packets, which should be
-        // sufficient.
-        3 *
-            sent_packet_manager_->EstimateMaxPacketsInFlight(
-                max_packet_length());
-  }
 }
 
 void QuicConnection::SetDiversificationNonce(const DiversificationNonce nonce) {