QUIC - FieldTrial parameters not do PreConnect if QUIC can do 0RTT.

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 485999cd2f32102cbc84c80a9be39a9a4f0ea706..3f271565efebc8721988807344f85389a9ad0b93 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -1122,6 +1122,8 @@ void IOThread::InitializeNetworkSessionParamsFromGlobals(
       &params->quic_close_sessions_on_ip_change);
   globals.quic_idle_connection_timeout_seconds.CopyToIfSet(
       &params->quic_idle_connection_timeout_seconds);
+  globals.quic_disable_preconnect_if_0rtt.CopyToIfSet(
+      &params->quic_disable_preconnect_if_0rtt);
 
   globals.origin_to_force_quic_on.CopyToIfSet(
       &params->origin_to_force_quic_on);
@@ -1259,6 +1261,8 @@ void IOThread::ConfigureQuicGlobals(
       globals->quic_idle_connection_timeout_seconds.set(
           idle_connection_timeout_seconds);
     }
+    globals->quic_disable_preconnect_if_0rtt.set(
+        ShouldQuicDisablePreConnectIfZeroRtt(quic_trial_params));
   }
 
   size_t max_packet_length = GetQuicMaxPacketLength(command_line,
@@ -1511,6 +1515,13 @@ int IOThread::GetQuicIdleConnectionTimeoutSeconds(
   return 0;
 }
 
+bool IOThread::ShouldQuicDisablePreConnectIfZeroRtt(
+    const VariationParameters& quic_trial_params) {
+  return base::LowerCaseEqualsASCII(
+      GetVariationParam(quic_trial_params, "disable_preconnect_if_0rtt"),
+      "true");
+}
+
 size_t IOThread::GetQuicMaxPacketLength(
     const base::CommandLine& command_line,
     const VariationParameters& quic_trial_params) {