Add PeerConnection IsClosed check.

webrtc/api/peerconnectionfactory.cc

Index: webrtc/api/peerconnectionfactory.cc
diff --git a/webrtc/api/peerconnectionfactory.cc b/webrtc/api/peerconnectionfactory.cc
index 745de3f214f748e179710128573e09dbb880fb1a..17537bfc61f34211d8cbe54c95852395b864619e 100644
--- a/webrtc/api/peerconnectionfactory.cc
+++ b/webrtc/api/peerconnectionfactory.cc
@@ -311,6 +311,13 @@ webrtc::MediaControllerInterface* PeerConnectionFactory::CreateMediaController(
                                           channel_manager_.get());
 }
 
+cricket::TransportController* PeerConnectionFactory::CreateTransportController(
+    cricket::PortAllocator* port_allocator) {
+  RTC_DCHECK(signaling_thread_->IsCurrent());
+  return new cricket::TransportController(signaling_thread_, network_thread_,
+                                          port_allocator);
+}
+
 rtc::Thread* PeerConnectionFactory::signaling_thread() {
   // This method can be called on a different thread when the factory is
   // created in CreatePeerConnectionFactory().