Early connection migration in QUIC.

net/quic/quic_stream_factory.h

Index: net/quic/quic_stream_factory.h
diff --git a/net/quic/quic_stream_factory.h b/net/quic/quic_stream_factory.h
index d76b6864ed30d757411c577f08845f25cb9af345..239e441ff529534f2d100ddeceb4a437be21f722 100644
--- a/net/quic/quic_stream_factory.h
+++ b/net/quic/quic_stream_factory.h
@@ -153,6 +153,7 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
       bool disable_quic_on_timeout_with_open_streams,
       int idle_connection_timeout_seconds,
       bool migrate_sessions_on_network_change,
+      bool migrate_sessions_early,
       const QuicTagVector& connection_options);
   ~QuicStreamFactory() override;
 
@@ -508,6 +509,10 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
   // interface changes.
   const bool migrate_sessions_on_network_change_;
 
+  // Set if early migration should be attempted when the connection
+  // experiences poor connectivity.
+  const bool migrate_sessions_early_;
+
   // Each profile will (probably) have a unique port_seed_ value.  This value
   // is used to help seed a pseudo-random number generator (PortSuggester) so
   // that we consistently (within this profile) suggest the same ephemeral