Enable the bayesian bitrate estimator by default.

webrtc/modules/congestion_controller/delay_based_bwe.h

Index: webrtc/modules/congestion_controller/delay_based_bwe.h
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe.h b/webrtc/modules/congestion_controller/delay_based_bwe.h
index 5ae60f7d21255480eb95fe2ebb65c64087f60434..c4713108201e79b347401af5c3290fef7f076c05 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe.h
+++ b/webrtc/modules/congestion_controller/delay_based_bwe.h
@@ -17,7 +17,6 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
-#include "webrtc/base/rate_statistics.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/congestion_controller/median_slope_estimator.h"
 #include "webrtc/modules/congestion_controller/probe_bitrate_estimator.h"
@@ -77,8 +76,6 @@ class DelayBasedBwe {
     int64_t prev_time_ms_;
     float bitrate_estimate_;
     float bitrate_estimate_var_;
-    RateStatistics old_estimator_;
-    const bool in_experiment_;
   };
 
   Result IncomingPacketFeedback(const PacketFeedback& packet_feedback);