Update from https://crrev.com/307330

net/quic/quic_server_session.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_server_session.h"
 
 #include "base/logging.h"
 #include "net/quic/crypto/cached_network_parameters.h"
 #include "net/quic/quic_connection.h"
 #include "net/quic/quic_flags.h"
@@ skipping 65 matching lines @@
 void QuicServerSession::OnWriteBlocked() {
   QuicSession::OnWriteBlocked();
   visitor_->OnWriteBlocked(connection());
 }
 
 void QuicServerSession::OnCongestionWindowChange(QuicTime now) {
   if (connection()->version() <= QUIC_VERSION_21) {
     return;
   }
 
+  // Only send updates when the application has no data to write.
+  if (HasDataToWrite()) {
+    return;
+  }
+
   // If not enough time has passed since the last time we sent an update to the
   // client, or not enough packets have been sent, then return early.
   const QuicSentPacketManager& sent_packet_manager =
       connection()->sent_packet_manager();
   int64 srtt_ms =
       sent_packet_manager.GetRttStats()->smoothed_rtt().ToMilliseconds();
   int64 now_ms = now.Subtract(last_scup_time_).ToMilliseconds();
   int64 packets_since_last_scup =
       connection()->sequence_number_of_last_sent_packet() -
       last_scup_sequence_number_;
@@ skipping 91 matching lines @@
 QuicDataStream* QuicServerSession::CreateOutgoingDataStream() {
   DLOG(ERROR) << "Server push not yet supported";
   return nullptr;
 }
 
 QuicCryptoServerStream* QuicServerSession::GetCryptoStream() {
   return crypto_stream_.get();
 }
 
 }  // namespace net