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 aa16ce630926c25fcc5d2a8608d558c2e1fd9218..ef01fd0a96e6209a93aec69912bd9cf9392eaf8e 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -209,6 +209,7 @@ class IOThread : public content::BrowserThreadDelegate {
     Optional<net::QuicVersionVector> quic_supported_versions;
     Optional<net::HostPortPair> origin_to_force_quic_on;
     Optional<bool> quic_close_sessions_on_ip_change;
+    Optional<bool> quic_migrate_sessions_on_net_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
@@ -421,6 +422,11 @@ class IOThread : public content::BrowserThreadDelegate {
   static bool ShouldQuicCloseSessionsOnIpChange(
       const VariationParameters& quic_trial_params);
 
+  // Returns true if QUIC should migrate sessions when primary network
+  // changes.
+  static bool ShouldQuicMigrateSessionsOnNetChange(
+      const VariationParameters& quic_trial_params);
+
   // Returns the maximum length for QUIC packets, based on any flags in
   // |command_line| or the field trial.  Returns 0 if there is an error
   // parsing any of the options, or if the default value should be used.