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 b8639142c234fe3a2e818b6eecc86a16a11cd80c..47f7b0b92ce35732f04f50d5c0fb00a715e3a3e2 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -571,6 +571,7 @@ 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),
@@ -620,6 +621,8 @@ 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),
@@ -660,8 +663,8 @@ QuicStreamFactory::QuicStreamFactory(
         new PropertiesBasedQuicServerInfoFactory(http_server_properties_));
   }
 
-  DCHECK(
-      !(close_sessions_on_ip_change_ && migrate_sessions_on_network_change_));
+  DCHECK(!close_sessions_on_ip_change_ || !migrate_sessions_on_network_change_);
+  DCHECK(migrate_sessions_on_network_change_ || !migrate_sessions_early_);

[Ryan Hamilton, 2016/02/02 04:19:59]

Can you add comments for these two blocks? These expressions are not immediately
understandable.

[Jana, 2016/02/02 06:53:53]

Done.

   if (migrate_sessions_on_network_change_) {
     NetworkChangeNotifier::AddNetworkObserver(this);
   } else if (close_sessions_on_ip_change_) {
@@ -1240,7 +1243,7 @@ void QuicStreamFactory::MaybeMigrateOrCloseSessions(
 
 void QuicStreamFactory::MaybeMigrateSessionEarly(

[Ryan Hamilton, 2016/02/02 04:19:59]

Was this landed post-review, or did I miss it in the previous CL?

[Jana, 2016/02/02 06:53:53]

This got added post-LGTM, and I am pretty sure it was due to some git magic that
I f***ed up. I most certainly didn't intend to add this code in, since it wasn't
getting used. Apologies.

     QuicChromiumClientSession* session) {
-  if (session->GetNumActiveStreams() == 0) {
+  if (!migrate_sessions_early_ || (session->GetNumActiveStreams() == 0)) {
     return;
   }
   NetworkChangeNotifier::NetworkHandle current_network =