Handle BW drop in ALR region and initiate probing

webrtc/modules/congestion_controller/probe_controller.h

 /*
  *  Copyright (c) 2016 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 35 matching lines @@
     kProbingComplete,
   };
   rtc::CriticalSection critsect_;
   PacedSender* const pacer_;
   Clock* const clock_;
   State state_ GUARDED_BY(critsect_);
   int min_bitrate_to_probe_further_bps_ GUARDED_BY(critsect_);
   int64_t time_last_probing_initiated_ms_ GUARDED_BY(critsect_);
   int estimated_bitrate_bps_ GUARDED_BY(critsect_);
   int max_bitrate_bps_ GUARDED_BY(critsect_);
+  int64_t last_alr_probing_time_ GUARDED_BY(critsect_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(ProbeController);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_CONGESTION_CONTROLLER_PROBE_CONTROLLER_H_