Do not switch to a high-cost connection that is not receiving

webrtc/p2p/base/port.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 535 matching lines @@
   // the current time, which is compared against various timeouts.
   void UpdateState(int64_t now);
 
   // Called when this connection should try checking writability again.
   int64_t last_ping_sent() const { return last_ping_sent_; }
   void Ping(int64_t now);
   void ReceivedPingResponse(int rtt, const std::string& request_id);
   int64_t last_ping_response_received() const {
     return last_ping_response_received_;
   }
+  // Used to check if any STUN ping response has been received.
+  int rtt_samples() const { return rtt_samples_; }
 
   // Called whenever a valid ping is received on this connection.  This is
   // public because the connection intercepts the first ping for us.
   int64_t last_ping_received() const { return last_ping_received_; }
   void ReceivedPing();
   // Handles the binding request; sends a response if this is a valid request.
   void HandleBindingRequest(IceMessage* msg);
 
   int64_t last_data_received() const { return last_data_received_; }
 
@@ skipping 148 matching lines @@
            const rtc::PacketOptions& options) override;
   int GetError() override { return error_; }
 
  private:
   int error_ = 0;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_PORT_H_