Update from https://crrev.com/307330

net/tools/quic/quic_server_session.cc

Index: net/tools/quic/quic_server_session.cc
diff --git a/net/tools/quic/quic_server_session.cc b/net/tools/quic/quic_server_session.cc
index 9db23659601c3202bcb76c75dc9c5c6ea90f44df..6e64da50c9057e0144af2b90b5ce77e86a00c394 100644
--- a/net/tools/quic/quic_server_session.cc
+++ b/net/tools/quic/quic_server_session.cc
@@ -84,6 +84,11 @@ void QuicServerSession::OnCongestionWindowChange(QuicTime now) {
     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 =