Revert of QUIC - enable "delay_tcp_race" parameter by default. This feature showed

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 f99b68f46e99323d399c51155d403593fa46d56b..7827dcca2bdc39613b80b2ee153ec93dfcec891b 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.h
+++ b/ios/chrome/browser/ios_chrome_io_thread.h
@@ -156,6 +156,7 @@
     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;
@@ -327,6 +328,10 @@
   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(