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 76af6c7c3d2669830665c77731d3dfd0e661651d..174bce599e3940db4754c8815d5910c3194ac1a5 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h
@@ -137,11 +137,13 @@ class WebRtcSession : public AudioProviderInterface,
     ERROR_TRANSPORT = 2,  // transport error of some kind
   };
 
-  WebRtcSession(webrtc::MediaControllerInterface* media_controller,
-                rtc::Thread* network_thread,
-                rtc::Thread* worker_thread,
-                rtc::Thread* signaling_thread,
-                cricket::PortAllocator* port_allocator);
+  WebRtcSession(
+      webrtc::MediaControllerInterface* media_controller,
+      rtc::Thread* network_thread,
+      rtc::Thread* worker_thread,
+      rtc::Thread* signaling_thread,
+      cricket::PortAllocator* port_allocator,
+      std::unique_ptr<cricket::TransportController> transport_controller);
   virtual ~WebRtcSession();
 
   // These are const to allow them to be called from const methods.