When doing continual gathering, remove local candidates when a network is dropped.

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 e83879f3b79b09cd0730534d364ed146de27d32a..e73861965e538e0ab8e09907d56b63241547c4b7 100644
--- a/webrtc/p2p/base/portinterface.h
+++ b/webrtc/p2p/base/portinterface.h
@@ -104,6 +104,9 @@ class PortInterface {
   // any usefulness.
   sigslot::signal1<PortInterface*> SignalDestroyed;
 
+  // Signaled when the network used by this port becomes inactive.
+  sigslot::signal1<PortInterface*> SignalNetworkInactive;
+
   // Signaled when Port discovers ice role conflict with the peer.
   sigslot::signal1<PortInterface*> SignalRoleConflict;