QUIC - Add back to code to experiment with delay_tcp_race. By default,

ios/chrome/browser/ios_chrome_io_thread.h

Index: ios/chrome/browser/ios_chrome_io_thread.h
diff --git a/ios/chrome/browser/ios_chrome_io_thread.h b/ios/chrome/browser/ios_chrome_io_thread.h
index 3b4749ee1c43d05893cf4ff0b3c6c1168ad94841..dc45330ea70d45398d4ee11104918c77fe2be836 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.h
+++ b/ios/chrome/browser/ios_chrome_io_thread.h
@@ -155,6 +155,7 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
     Optional<int> quic_max_number_of_lossy_connections;
     Optional<float> quic_packet_loss_threshold;
     Optional<int> quic_socket_receive_buffer_size;
+    Optional<bool> quic_delay_tcp_race;
     Optional<size_t> quic_max_packet_length;
     net::QuicTagVector quic_connection_options;
     Optional<std::string> quic_user_agent_id;
@@ -318,6 +319,10 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
   static int GetQuicSocketReceiveBufferSize(
       const VariationParameters& quic_trial_params);
 
+  // Returns true if QUIC should delay TCP connection when QUIC works.
+  static bool ShouldQuicDelayTcpRace(
+      const VariationParameters& quic_trial_params);
+
   // Returns true if QUIC should close sessions when any of the client's
   // IP addresses change.
   static bool ShouldQuicCloseSessionsOnIpChange(