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

ios/chrome/browser/ios_chrome_io_thread.mm

Index: ios/chrome/browser/ios_chrome_io_thread.mm
diff --git a/ios/chrome/browser/ios_chrome_io_thread.mm b/ios/chrome/browser/ios_chrome_io_thread.mm
index f998fd68b371e0b8f558cc17b01f41e75a7c119b..fa32840b393a0f0b2da18375967c8ffc203884c0 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.mm
+++ b/ios/chrome/browser/ios_chrome_io_thread.mm
@@ -663,6 +663,7 @@ void IOSChromeIOThread::InitializeNetworkSessionParamsFromGlobals(
       &params->quic_packet_loss_threshold);
   globals.quic_socket_receive_buffer_size.CopyToIfSet(
       &params->quic_socket_receive_buffer_size);
+  globals.quic_delay_tcp_race.CopyToIfSet(&params->quic_delay_tcp_race);
   params->enable_quic_port_selection = false;
   globals.quic_max_packet_length.CopyToIfSet(&params->quic_max_packet_length);
   globals.quic_user_agent_id.CopyToIfSet(&params->quic_user_agent_id);
@@ -768,6 +769,7 @@ void IOSChromeIOThread::ConfigureQuicGlobals(
     if (receive_buffer_size != 0) {
       globals->quic_socket_receive_buffer_size.set(receive_buffer_size);
     }
+    globals->quic_delay_tcp_race.set(ShouldQuicDelayTcpRace(quic_trial_params));
     float load_server_info_timeout_srtt_multiplier =
         GetQuicLoadServerInfoTimeoutSrttMultiplier(quic_trial_params);
     if (load_server_info_timeout_srtt_multiplier != 0) {
@@ -930,6 +932,12 @@ int IOSChromeIOThread::GetQuicSocketReceiveBufferSize(
   return 0;
 }
 
+bool IOSChromeIOThread::ShouldQuicDelayTcpRace(
+    const VariationParameters& quic_trial_params) {
+  return base::LowerCaseEqualsASCII(
+      GetVariationParam(quic_trial_params, "delay_tcp_race"), "true");
+}
+
 bool IOSChromeIOThread::ShouldQuicCloseSessionsOnIpChange(
     const VariationParameters& quic_trial_params) {
   return base::LowerCaseEqualsASCII(