Use continual gathering to restore backup connections

webrtc/p2p/base/port.h

Index: webrtc/p2p/base/port.h
diff --git a/webrtc/p2p/base/port.h b/webrtc/p2p/base/port.h
index 06efd2d3c235c4e976fda6f610c187741ac7542f..e15aa0010eeaf136ab5b68bf867a063e763e3332 100644
--- a/webrtc/p2p/base/port.h
+++ b/webrtc/p2p/base/port.h
@@ -142,6 +142,8 @@ class Port : public PortInterface, public rtc::MessageHandler,
   virtual const std::string& Type() const { return type_; }
   virtual rtc::Network* Network() const { return network_; }
 
+  virtual void FailAndDestroyConnections();
+
   // Methods to set/get ICE role and tiebreaker values.
   IceRole GetIceRole() const { return ice_role_; }
   void SetIceRole(IceRole role) { ice_role_ = role; }
@@ -161,6 +163,8 @@ class Port : public PortInterface, public rtc::MessageHandler,
     factory_ = factory;
   }
 
+  void CloseAndSignalCandidateRemovals();
+
   // For debugging purposes.
   const std::string& content_name() const { return content_name_; }
   void set_content_name(const std::string& content_name) {
@@ -195,6 +199,10 @@ class Port : public PortInterface, public rtc::MessageHandler,
   // are discovered that belong to port SignalAddressReady is fired.
   sigslot::signal2<Port*, const Candidate&> SignalCandidateReady;
 
+  // Fired when candidates need to be signaled for removing on the remote side.
+  sigslot::signal2<Port*, const std::vector<Candidate>&>
+      SignalCandidatesRemoved;
+
   // Provides all of the above information in one handy object.
   virtual const std::vector<Candidate>& Candidates() const {
     return candidates_;
@@ -397,6 +405,7 @@ class Port : public PortInterface, public rtc::MessageHandler,
   // Information to use when going through a proxy.
   std::string user_agent_;
   rtc::ProxyInfo proxy_;
+  bool closed_ = false;
 
   // A virtual cost perceived by the user, usually based on the network type
   // (WiFi. vs. Cellular). It takes precedence over the priority when