Do not switch best connection on the controlled side too frequently

webrtc/p2p/base/p2ptransportchannel.h

Index: webrtc/p2p/base/p2ptransportchannel.h
diff --git a/webrtc/p2p/base/p2ptransportchannel.h b/webrtc/p2p/base/p2ptransportchannel.h
index ada3ecfb8bb2deeb6bc5d9120eb1647d7cd1a1da..fd5d62c98ebce80f8b4a3d81eb75f5b918a9d142 100644
--- a/webrtc/p2p/base/p2ptransportchannel.h
+++ b/webrtc/p2p/base/p2ptransportchannel.h
@@ -115,7 +115,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   int GetError() override { return error_; }
   bool GetStats(std::vector<ConnectionInfo>* stats) override;
 
-  const Connection* best_connection() const { return best_connection_; }
+  const Connection* selected_connection() const { return selected_connection_; }
   void set_incoming_only(bool value) { incoming_only_ = value; }
 
   // Note: This is only for testing purpose.
@@ -208,7 +208,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   void UpdateConnectionStates();
   void RequestSort();
   void SortConnections();
-  void SwitchBestConnectionTo(Connection* conn);
+  void SwitchSelectedConnection(Connection* conn);
   void UpdateState();
   void HandleAllTimedOut();
   void MaybeStopPortAllocatorSessions();
@@ -258,8 +258,10 @@ class P2PTransportChannel : public TransportChannelImpl,
   void OnSort();
   void OnCheckAndPing();
 
+  bool ShouldSwitchOnNominatedOrDataReceived(Connection* new_connection) const;

[pthatcher1, 2016/06/17 00:27:11]

I still think ShouldSwitchSelectedCandidate makes more sense.  We don't need why
to switch in the method name.

[honghaiz3, 2016/06/17 19:18:18]

Done.

+
   void PruneConnections();
-  Connection* best_nominated_connection() const;
+  Connection* selected_nominated_connection() const;
   bool IsBackupConnection(Connection* conn) const;
 
   Connection* FindConnectionToPing(int64_t now);
@@ -300,7 +302,7 @@ class P2PTransportChannel : public TransportChannelImpl,
   std::vector<PortInterface *> ports_;
 
   // |connections_| is a sorted list with the first one always be the
-  // |best_connection_| when it's not nullptr. The combination of
+  // |selected_connection_| when it's not nullptr. The combination of
   // |pinged_connections_| and |unpinged_connections_| has the same
   // connections as |connections_|. These 2 sets maintain whether a
   // connection should be pinged next or not.
@@ -308,11 +310,15 @@ class P2PTransportChannel : public TransportChannelImpl,
   std::set<Connection*> pinged_connections_;
   std::set<Connection*> unpinged_connections_;
 
-  Connection* best_connection_;
+  Connection* selected_connection_ = nullptr;
+
+  // Connection most recently nominated by the controlling agent.
+  // This should be used only at the controlled side.
+  Connection* last_nominated_connection_ = nullptr;
+  // The connection on which the data was most recently received.
+  // Should only be used at the controlled side.
+  Connection* last_receiving_connection_ = nullptr;
 
-  // Connection selected by the controlling agent. This should be used only
-  // at controlled side when protocol type is RFC5245.
-  Connection* pending_best_connection_;
   std::vector<RemoteCandidate> remote_candidates_;
   bool sort_dirty_;  // indicates whether another sort is needed right now
   bool had_connection_ = false;  // if connections_ has ever been nonempty