Relanding "Pass time constant to bwe smoothing filter."

webrtc/modules/congestion_controller/delay_based_bwe.cc

Index: webrtc/modules/congestion_controller/delay_based_bwe.cc
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe.cc b/webrtc/modules/congestion_controller/delay_based_bwe.cc
index 78bc7f0e6e4702210ba3709cdc17017930f4608c..04dadc489c0afac2a17e88510e2ea4397b5e9f4b 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe.cc
+++ b/webrtc/modules/congestion_controller/delay_based_bwe.cc
@@ -180,7 +180,8 @@ DelayBasedBwe::DelayBasedBwe(Clock* clock)
       trendline_window_size_(kDefaultTrendlineWindowSize),
       trendline_smoothing_coeff_(kDefaultTrendlineSmoothingCoeff),
       trendline_threshold_gain_(kDefaultTrendlineThresholdGain),
-      in_trendline_experiment_(TrendlineFilterExperimentIsEnabled()) {
+      in_trendline_experiment_(TrendlineFilterExperimentIsEnabled()),
+      probing_interval_estimator_(&rate_control_) {
   if (in_trendline_experiment_) {
     ReadTrendlineFilterExperimentParameters(&trendline_window_size_,
                                             &trendline_smoothing_coeff_,
@@ -330,4 +331,8 @@ void DelayBasedBwe::SetMinBitrate(int min_bitrate_bps) {
   // be called from the network thread in the future.
   rate_control_.SetMinBitrate(min_bitrate_bps);
 }
+
+int64_t DelayBasedBwe::GetProbingIntervalMs() const {
+  return probing_interval_estimator_.GetIntervalMs();
+}
 }  // namespace webrtc