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

net/quic/quic_connection.h

Index: net/quic/quic_connection.h
diff --git a/net/quic/quic_connection.h b/net/quic/quic_connection.h
index 4b23ba956f614275e1cdfc29609f9a7250d6da24..6b43e50a74ef9af4eb2cd79d39076a13db35150a 100644
--- a/net/quic/quic_connection.h
+++ b/net/quic/quic_connection.h
@@ -505,8 +505,9 @@ class NET_EXPORT_PRIVATE QuicConnection
   // Otherwise, it will reschedule the timeout alarm.
   void CheckForTimeout();
 
-  // Sends a ping, and resets the ping alarm.
-  void SendPing();
+  // Sends a ping, and resets the ping alarm. If |force| is false,
+  // only sends a ping if the retransmission alarm is not running.
+  void SendPing(bool force);
 
   // Sets up a packet with an QuicAckFrame and sends it out.
   void SendAck();