Adds plumbing for always requiring handshake confirmation in QUIC.

net/http/http_network_session.h

Index: net/http/http_network_session.h
diff --git a/net/http/http_network_session.h b/net/http/http_network_session.h
index f62232a22a63982092d6560020a6be12585e5258..da8ac72a28a908893c0f916eb62e23fd4729458c 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -111,6 +111,7 @@ class NET_EXPORT HttpNetworkSession
     bool enable_quic;
     bool enable_quic_port_selection;
     bool enable_quic_time_based_loss_detection;
+    bool quic_always_require_handshake_confirmation;
     HostPortPair origin_to_force_quic_on;
     QuicClock* quic_clock;  // Will be owned by QuicStreamFactory.
     QuicRandom* quic_random;