Implement Theil-Sen's method for fitting a line to noisy data (used in bandwidth estimation).

webrtc/modules/congestion_controller/delay_based_bwe.h

Index: webrtc/modules/congestion_controller/delay_based_bwe.h
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe.h b/webrtc/modules/congestion_controller/delay_based_bwe.h
index 0f1472e6729dbb976887caf30731d209af9a42a0..1629ac367e44d7083024224d05c699b760df3a41 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe.h
+++ b/webrtc/modules/congestion_controller/delay_based_bwe.h
@@ -20,6 +20,7 @@
 #include "webrtc/base/rate_statistics.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/congestion_controller/probe_bitrate_estimator.h"
+#include "webrtc/modules/congestion_controller/theil_sen_estimator.h"
 #include "webrtc/modules/congestion_controller/trendline_estimator.h"
 #include "webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h"
 #include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
@@ -82,12 +83,15 @@ class DelayBasedBwe {
                       int64_t now_ms,
                       rtc::Optional<uint32_t> acked_bitrate_bps,
                       uint32_t* target_bitrate_bps);
+  const bool in_trendline_experiment_;
+  const bool in_theil_sen_experiment_;
 
   rtc::ThreadChecker network_thread_;
   Clock* const clock_;
   std::unique_ptr<InterArrival> inter_arrival_;
   std::unique_ptr<OveruseEstimator> kalman_estimator_;
   std::unique_ptr<TrendlineEstimator> trendline_estimator_;
+  std::unique_ptr<TheilSenEstimator> theil_sen_estimator_;
   OveruseDetector detector_;
   BitrateEstimator receiver_incoming_bitrate_;
   int64_t last_update_ms_;
@@ -98,7 +102,8 @@ class DelayBasedBwe {
   size_t trendline_window_size_;
   double trendline_smoothing_coeff_;
   double trendline_threshold_gain_;
-  const bool in_trendline_experiment_;
+  size_t theil_sen_window_size_;
+  double theil_sen_threshold_gain_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(DelayBasedBwe);
 };