Make the BWE threshold adaptive.

webrtc/modules/remote_bitrate_estimator/overuse_detector.h

Index: webrtc/modules/remote_bitrate_estimator/overuse_detector.h
diff --git a/webrtc/modules/remote_bitrate_estimator/overuse_detector.h b/webrtc/modules/remote_bitrate_estimator/overuse_detector.h
index 8269368ae04e6f387b897730edea3cc3e59833db..c31922236cd849afcf21e8f4cf2371aba2f41cdf 100644
--- a/webrtc/modules/remote_bitrate_estimator/overuse_detector.h
+++ b/webrtc/modules/remote_bitrate_estimator/overuse_detector.h
@@ -20,10 +20,12 @@
 namespace webrtc {
 enum RateControlRegion;
 
+bool AdaptiveThresholdExperimentIsEnabled();
+
 class OveruseDetector {
  public:
   explicit OveruseDetector(const OverUseDetectorOptions& options);
-  ~OveruseDetector();
+  virtual ~OveruseDetector();
 
   // Update the detection state based on the estimated inter-arrival time delta
   // offset. |timestamp_delta| is the delta between the last timestamp which the
@@ -39,15 +41,24 @@ class OveruseDetector {
   // Returns the current detector state.
   BandwidthUsage State() const;
 
-  // Sets the current rate-control region as decided by RemoteRateControl. This
-  // affects the sensitivity of the detector.
-  void SetRateControlRegion(webrtc::RateControlRegion region);
+  virtual void InitializeExperiment();

[pbos-webrtc, 2015/07/06 10:01:40]

Don't like this being virtual, pref. checking in_experiment_ in subclasses and
applying experiment magic, then everything should be ready-to-rock after
construction.

[stefan-webrtc, 2015/07/06 10:54:26]

Done.

[pbos-webrtc, 2015/07/06 11:13:26]

This is still virtual, does it even have to be externally visible or can it go
under private:? or protected:?

[stefan-webrtc, 2015/07/06 12:16:13]

Done.

+
+ protected:
+  double threshold_;
+  double k_up_;
+  double k_down_;
+  bool experiment_set_;
+  bool in_experiment_;
 
  private:
+  void UpdateThreshold(double modified_offset, int64_t now_ms);
+  bool AdaptiveThresholdExperimentIsEnabled();
+  bool ReadExperimentConstants(double* k_up, double* k_down) const;
+
   // Must be first member variable. Cannot be const because we need to be
   // copyable.
   webrtc::OverUseDetectorOptions options_;
-  double threshold_;
+  int64_t last_update_ms_;
   double prev_offset_;
   double time_over_using_;
   int overuse_counter_;