Use the default QUIC initial CWND.

net/quic/quic_stream_factory.cc

Index: net/quic/quic_stream_factory.cc
diff --git a/net/quic/quic_stream_factory.cc b/net/quic/quic_stream_factory.cc
index 40f294821850e0a6fbffa5c9dc5a1d0fbb58d13c..dbb6de2a755431946eba2deef7237dca27e9e263 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -261,6 +261,9 @@ QuicStreamFactory::QuicStreamFactory(
   config_.set_idle_connection_state_lifetime(
       QuicTime::Delta::FromSeconds(30),
       QuicTime::Delta::FromSeconds(30));
+  config_.set_server_initial_congestion_window(kDefaultInitialWindow,
+                                               kDefaultInitialWindow);
+
   cannoncial_suffixes_.push_back(string(".c.youtube.com"));
   cannoncial_suffixes_.push_back(string(".googlevideo.com"));
 }