Remove ports that are not used by any channel after timeout

webrtc/p2p/base/portinterface.h

Index: webrtc/p2p/base/portinterface.h
diff --git a/webrtc/p2p/base/portinterface.h b/webrtc/p2p/base/portinterface.h
index 38945f9e1305fb68a05287baacb4cda507aba477..f6b674243f51ea20505478fe2e92c55cb6dccc0d 100644
--- a/webrtc/p2p/base/portinterface.h
+++ b/webrtc/p2p/base/portinterface.h
@@ -55,6 +55,11 @@ class PortInterface {
 
   virtual bool SupportsProtocol(const std::string& protocol) const = 0;
 
+  // Called when this port starts to be used by a channel.
+  virtual void StartBeingUsed() = 0;
+  // Called when this port stops being used by a channel.
+  virtual void StopBeingUsed() = 0;
+
   // PrepareAddress will attempt to get an address for this port that other
   // clients can send to.  It may take some time before the address is ready.
   // Once it is ready, we will send SignalAddressReady.  If errors are