Wire up transport sequence number / send time callbacks to webrtc via libjingle.

webrtc/p2p/base/transportchannel.h

Index: webrtc/p2p/base/transportchannel.h
diff --git a/webrtc/p2p/base/transportchannel.h b/webrtc/p2p/base/transportchannel.h
index afdba4296936d3d12c05e657ed41a3bd6c521140..42b864a4291d904cf0798ca979bbef91b969d0ca 100644
--- a/webrtc/p2p/base/transportchannel.h
+++ b/webrtc/p2p/base/transportchannel.h
@@ -136,6 +136,9 @@ class TransportChannel : public sigslot::has_slots<> {
   sigslot::signal5<TransportChannel*, const char*,
                    size_t, const rtc::PacketTime&, int> SignalReadPacket;
 
+  // Signalled each time a packet is sent on this channel.
+  sigslot::signal2<TransportChannel*, const rtc::SentPacket&> SignalSentPacket;
+
   // This signal occurs when there is a change in the way that packets are
   // being routed, i.e. to a different remote location. The candidate
   // indicates where and how we are currently sending media.