Add the last_sent_packet_id to the candidate pair change signal

webrtc/p2p/base/dtlstransportchannel.h

Index: webrtc/p2p/base/dtlstransportchannel.h
diff --git a/webrtc/p2p/base/dtlstransportchannel.h b/webrtc/p2p/base/dtlstransportchannel.h
index 0c6b303d59ed19dc4e8cf9d83702b214798d8f19..96ea29fa5d3038dbad7117b427769fee29db39c4 100644
--- a/webrtc/p2p/base/dtlstransportchannel.h
+++ b/webrtc/p2p/base/dtlstransportchannel.h
@@ -218,7 +218,8 @@ class DtlsTransportChannelWrapper : public TransportChannelImpl {
   void OnRouteChange(TransportChannel* channel, const Candidate& candidate);
   void OnSelectedCandidatePairChanged(
       TransportChannel* channel,
-      CandidatePairInterface* selected_candidate_pair);
+      CandidatePairInterface* selected_candidate_pair,
+      int last_sent_packet_id);
   void OnConnectionRemoved(TransportChannelImpl* channel);
   void Reconnect();