Make the BWE threshold adaptive.

webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h

Index: webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
diff --git a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
index 56f1c1a8661fbb6b524f6f73f6b1169103a8d9ff..80fd73e8081e2bf22eb6df7c0184ea56726479ff 100644
--- a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
+++ b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
@@ -40,8 +40,7 @@ class AimdRateControl : public RemoteRateControl {
   uint32_t LatestEstimate() const override;
   uint32_t UpdateBandwidthEstimate(int64_t now_ms) override;
   void SetRtt(int64_t rtt) override;
-  RateControlRegion Update(const RateControlInput* input,
-                           int64_t now_ms) override;
+  void Update(const RateControlInput* input, int64_t now_ms) override;
   void SetEstimate(int bitrate_bps, int64_t now_ms) override;
 
  private:
@@ -72,7 +71,6 @@ class AimdRateControl : public RemoteRateControl {
   float avg_max_bitrate_kbps_;
   float var_max_bitrate_kbps_;
   RateControlState rate_control_state_;
-  RateControlState came_from_state_;
   RateControlRegion rate_control_region_;
   int64_t time_last_bitrate_change_;
   RateControlInput current_input_;
@@ -82,6 +80,7 @@ class AimdRateControl : public RemoteRateControl {
   float beta_;
   int64_t rtt_;
   int64_t time_of_last_log_;
+  bool in_experiment_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AimdRateControl);
 };