Perform probing on network route change.

webrtc/modules/congestion_controller/include/congestion_controller.h

 /*
  *  Copyright (c) 2012 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 150 matching lines @@
   bool IsSendQueueFull() const;
   bool IsNetworkDown() const;
   bool HasNetworkParametersToReportChanged(uint32_t bitrate_bps,
                                            uint8_t fraction_loss,
                                            int64_t rtt);
   Clock* const clock_;
   Observer* const observer_;
   PacketRouter* const packet_router_;
   const std::unique_ptr<PacedSender> pacer_;
   const std::unique_ptr<BitrateController> bitrate_controller_;
-  const std::unique_ptr<ProbeController> probe_controller_;
+  std::unique_ptr<ProbeController> probe_controller_;
   const std::unique_ptr<RateLimiter> retransmission_rate_limiter_;
   WrappingBitrateEstimator remote_bitrate_estimator_;
   RemoteEstimatorProxy remote_estimator_proxy_;
   TransportFeedbackAdapter transport_feedback_adapter_;
   int min_bitrate_bps_;
   int max_bitrate_bps_;
   rtc::CriticalSection critsect_;
   uint32_t last_reported_bitrate_bps_ GUARDED_BY(critsect_);
   uint8_t last_reported_fraction_loss_ GUARDED_BY(critsect_);
   int64_t last_reported_rtt_ GUARDED_BY(critsect_);
   NetworkState network_state_ GUARDED_BY(critsect_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(CongestionController);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_INCLUDE_CONGESTION_CONTROLLER_H_