Early connection migration in QUIC.

net/quic/quic_stream_factory.cc

Index: net/quic/quic_stream_factory.cc
diff --git a/net/quic/quic_stream_factory.cc b/net/quic/quic_stream_factory.cc
index 76605a53e81ff5137fc97d9fb54699712f06335d..4e13167b35d39cab20151f7322092d2ef8a79790 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -585,6 +585,7 @@ QuicStreamFactory::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)
     : require_confirmation_(true),
       host_resolver_(host_resolver),
@@ -634,6 +635,8 @@ QuicStreamFactory::QuicStreamFactory(
       migrate_sessions_on_network_change_(
           migrate_sessions_on_network_change &&
           NetworkChangeNotifier::AreNetworkHandlesSupported()),
+      migrate_sessions_early_(migrate_sessions_early &&
+                              migrate_sessions_on_network_change_),
       port_seed_(random_generator_->RandUint64()),
       check_persisted_supports_quic_(true),
       has_initialized_data_(false),
@@ -674,8 +677,12 @@ QuicStreamFactory::QuicStreamFactory(
         new PropertiesBasedQuicServerInfoFactory(http_server_properties_));
   }
 
-  DCHECK(
-      !(close_sessions_on_ip_change_ && migrate_sessions_on_network_change_));
+  // migrate_sessions_early_ should only be set to true if
+  // migrate_sessions_on_network_change_ is set to true.
+  DCHECK(migrate_sessions_on_network_change_ || !migrate_sessions_early_);
+  // close_sessions_on_ip_change_ and migrate_sessions_on_network_change_ should
+  // never be simultaneously set to true.
+  DCHECK(!close_sessions_on_ip_change_ || !migrate_sessions_on_network_change_);
   if (migrate_sessions_on_network_change_) {
     NetworkChangeNotifier::AddNetworkObserver(this);
   } else if (close_sessions_on_ip_change_) {
@@ -1254,7 +1261,7 @@ void QuicStreamFactory::MaybeMigrateOrCloseSessions(
 
 void QuicStreamFactory::MaybeMigrateSessionEarly(
     QuicChromiumClientSession* session) {
-  if (session->GetNumActiveStreams() == 0) {
+  if (!migrate_sessions_early_ || (session->GetNumActiveStreams() == 0)) {
     return;
   }
   NetworkChangeNotifier::NetworkHandle current_network =