Relanding "Pass time constant to bwe smoothing filter."

webrtc/modules/congestion_controller/probing_interval_estimator.h

Index: webrtc/modules/congestion_controller/probing_interval_estimator.h
diff --git a/webrtc/modules/congestion_controller/probing_interval_estimator.h b/webrtc/modules/congestion_controller/probing_interval_estimator.h
index daa6b91a8cae7dc76b82bbc16a0c02ad45f7c345..993e0da5506bb8862b9ef33986af859a22f8d5ad 100644
--- a/webrtc/modules/congestion_controller/probing_interval_estimator.h
+++ b/webrtc/modules/congestion_controller/probing_interval_estimator.h
@@ -21,14 +21,16 @@ class ProbingIntervalEstimator {
  public:
   explicit ProbingIntervalEstimator(const AimdRateControl* aimd_rate_control);
 
-  ProbingIntervalEstimator(int min_interval_ms,
-                           int max_interval_ms,
+  ProbingIntervalEstimator(int64_t min_interval_ms,
+                           int64_t max_interval_ms,
+                           int64_t default_interval_ms,
                            const AimdRateControl* aimd_rate_control);
-  rtc::Optional<int> GetIntervalMs() const;
+  int64_t GetIntervalMs() const;
 
  private:
-  const int min_interval_ms_;
-  const int max_interval_ms_;
+  const int64_t min_interval_ms_;
+  const int64_t max_interval_ms_;
+  const int64_t default_interval_ms_;
   const AimdRateControl* const aimd_rate_control_;
   RTC_DISALLOW_COPY_AND_ASSIGN(ProbingIntervalEstimator);
 };