Add PeerConnection IsClosed check.

webrtc/api/webrtcsession.cc

Index: webrtc/api/webrtcsession.cc
diff --git a/webrtc/api/webrtcsession.cc b/webrtc/api/webrtcsession.cc
index 24eb5936386b6918c4026e4d44e9422d780321c4..7de504016a4235fb3ead6818edc927b17ed63d2e 100644
--- a/webrtc/api/webrtcsession.cc
+++ b/webrtc/api/webrtcsession.cc
@@ -1476,6 +1476,22 @@ void WebRtcSession::SetIceConnectionState(
   }
 }
 
+void WebRtcSession::SetTransportController(
+    cricket::TransportController* transport_controller) {
+  transport_controller_.reset(transport_controller);
+  transport_controller_->SetIceRole(cricket::ICEROLE_CONTROLLED);
+  transport_controller_->SignalConnectionState.connect(
+      this, &WebRtcSession::OnTransportControllerConnectionState);
+  transport_controller_->SignalReceiving.connect(
+      this, &WebRtcSession::OnTransportControllerReceiving);
+  transport_controller_->SignalGatheringState.connect(
+      this, &WebRtcSession::OnTransportControllerGatheringState);
+  transport_controller_->SignalCandidatesGathered.connect(
+      this, &WebRtcSession::OnTransportControllerCandidatesGathered);
+  transport_controller_->SignalCandidatesRemoved.connect(
+      this, &WebRtcSession::OnTransportControllerCandidatesRemoved);
+}
+
 void WebRtcSession::OnTransportControllerConnectionState(
     cricket::IceConnectionState state) {
   switch (state) {