Update from https://crrev.com/307330

net/quic/quic_server_session.cc

Index: net/quic/quic_server_session.cc
diff --git a/net/quic/quic_server_session.cc b/net/quic/quic_server_session.cc
index e0defd680efb35a5b3c736e9e80974434a249665..64857c0857679943bb031d441465701b3b761a8a 100644
--- a/net/quic/quic_server_session.cc
+++ b/net/quic/quic_server_session.cc
@@ -83,6 +83,11 @@ 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 =