QUIC congestion option that forces ICWND to 10. Not flag protected.

net/quic/congestion_control/tcp_cubic_sender_test.cc

Index: net/quic/congestion_control/tcp_cubic_sender_test.cc
diff --git a/net/quic/congestion_control/tcp_cubic_sender_test.cc b/net/quic/congestion_control/tcp_cubic_sender_test.cc
index ef2e1c0a2cf0ff5a68305f1ae2a209aa138b6635..d80c4f80a779221693ad89dacce2e8198fed0b13 100644
--- a/net/quic/congestion_control/tcp_cubic_sender_test.cc
+++ b/net/quic/congestion_control/tcp_cubic_sender_test.cc
@@ -9,6 +9,7 @@
 #include "net/quic/congestion_control/rtt_stats.h"
 #include "net/quic/congestion_control/tcp_cubic_sender.h"
 #include "net/quic/congestion_control/tcp_receiver.h"
+#include "net/quic/crypto/crypto_protocol.h"
 #include "net/quic/quic_utils.h"
 #include "net/quic/test_tools/mock_clock.h"
 #include "net/quic/test_tools/quic_config_peer.h"
@@ -612,6 +613,14 @@ TEST_F(TcpCubicSenderTest, ConfigureMaxInitialWindow) {
 
   sender_->SetFromConfig(config, true);
   EXPECT_EQ(2 * congestion_window, sender_->congestion_window());
+
+  // Verify that kCOPT: kIW10 forces the congestion window to the
+  // default of 10 regardless of ReceivedInitialWindow.
+  QuicTagVector options;
+  options.push_back(kIW10);
+  QuicConfigPeer::SetReceivedConnectionOptions(&config, options);
+  sender_->SetFromConfig(config, true);
+  EXPECT_EQ(congestion_window, sender_->congestion_window());
 }
 
 TEST_F(TcpCubicSenderTest, CongestionAvoidanceAtEndOfRecovery) {