Make the acceptable queue in the cwnd experiment configurable.

webrtc/modules/congestion_controller/include/send_side_congestion_controller.h

Index: webrtc/modules/congestion_controller/include/send_side_congestion_controller.h
diff --git a/webrtc/modules/congestion_controller/include/send_side_congestion_controller.h b/webrtc/modules/congestion_controller/include/send_side_congestion_controller.h
index 68213507a6c1d8308626d38cbd29a8dfaa5abf8a..1d576aaf00987a181aedda61363125aecd022242 100644
--- a/webrtc/modules/congestion_controller/include/send_side_congestion_controller.h
+++ b/webrtc/modules/congestion_controller/include/send_side_congestion_controller.h
@@ -160,7 +160,8 @@ class SendSideCongestionController : public CallStatsObserver,
   rtc::CriticalSection bwe_lock_;
   int min_bitrate_bps_ GUARDED_BY(bwe_lock_);
   std::unique_ptr<DelayBasedBwe> delay_based_bwe_ GUARDED_BY(bwe_lock_);
-  const bool in_cwnd_experiment_;
+  bool in_cwnd_experiment_;
+  int64_t accepted_queue_ms_;
   bool was_in_alr_;
 
   rtc::RaceChecker worker_race_;