Add PeerConnection IsClosed check.

webrtc/api/webrtcsession.h

Index: webrtc/api/webrtcsession.h
diff --git a/webrtc/api/webrtcsession.h b/webrtc/api/webrtcsession.h
index dd47229a61e1a5f55568a8ecb53e4e66c3450a95..5f71cbb65da5a03f53392dbb50ac51c940bc91c0 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h
@@ -321,6 +321,11 @@ class WebRtcSession : public AudioProviderInterface,
     metrics_observer_ = metrics_observer;
   }
 
+  // Set the transport controller and subscribe the Signals from the
+  // TransportController.
+  void SetTransportController(
+      cricket::TransportController* transport_controller);
+
   // Called when voice_channel_, video_channel_ and data_channel_ are created
   // and destroyed. As a result of, for example, setting a new description.
   sigslot::signal0<> SignalVoiceChannelCreated;