Allow IP migration.

net/quic/core/quic_server_session_base.h

Index: net/quic/core/quic_server_session_base.h
diff --git a/net/quic/core/quic_server_session_base.h b/net/quic/core/quic_server_session_base.h
index 0a14a56084198d3408af6247594e99fedc5a6500..983d849b38b1114b29b1e9da6510b1a7b97cdd7c 100644
--- a/net/quic/core/quic_server_session_base.h
+++ b/net/quic/core/quic_server_session_base.h
@@ -54,6 +54,10 @@ class NET_EXPORT_PRIVATE QuicServerSessionBase : public QuicSpdySession {
     // Called after the given connection is added to the time-wait std::list.
     virtual void OnConnectionAddedToTimeWaitList(
         QuicConnectionId connection_id) = 0;
+
+    // Called before a packet is going to be processed by |session|.
+    virtual void OnPacketBeingDispatchedToSession(
+        QuicServerSessionBase* session) = 0;
   };
 
   // Provides helper functions for the session.
@@ -142,6 +146,8 @@ class NET_EXPORT_PRIVATE QuicServerSessionBase : public QuicSpdySession {
 
   void set_server_push_enabled(bool enable) { server_push_enabled_ = enable; }
 
+  Visitor* visitor() { return visitor_; }
+
  private:
   friend class test::QuicServerSessionBasePeer;
   friend class test::QuicSimpleServerSessionPeer;