Migrates QUIC sessions to a new network when old network is (about to be) disconnected.

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index b7ca041b63978eeeddf1ec4473125169e29ce5d3..2844ef59ed6a392b79718791ec8029d9fc6dcb0a 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -239,6 +239,7 @@ class IOThread : public content::BrowserThreadDelegate {
     Optional<bool> quic_close_sessions_on_ip_change;
     Optional<int> quic_idle_connection_timeout_seconds;
     Optional<bool> quic_disable_preconnect_if_0rtt;
+    Optional<bool> quic_migrate_sessions_on_network_change;
     bool enable_user_alternate_protocol_ports;
     // NetErrorTabHelper uses |dns_probe_service| to send DNS probes when a
     // main frame load fails with a DNS error in order to provide more useful
@@ -459,6 +460,10 @@ class IOThread : public content::BrowserThreadDelegate {
 
   // Returns true if PreConnect should be disabled if QUIC can do 0RTT.
   static bool ShouldQuicDisablePreConnectIfZeroRtt(
+
+  // Returns true if QUIC should migrate sessions when primary network
+  // changes.
+  static bool ShouldQuicMigrateSessionsOnNetworkChange(
       const VariationParameters& quic_trial_params);
 
   // Returns the maximum length for QUIC packets, based on any flags in