Revert of Enable the bayesian bitrate estimator by default.

webrtc/modules/congestion_controller/delay_based_bwe.cc

Index: webrtc/modules/congestion_controller/delay_based_bwe.cc
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe.cc b/webrtc/modules/congestion_controller/delay_based_bwe.cc
index 3fa48c7a423d778d05244a7b4185fc682dfb9708..e8d9d21050f21d1b931999b758979b95ec953bcb 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe.cc
+++ b/webrtc/modules/congestion_controller/delay_based_bwe.cc
@@ -52,8 +52,13 @@
 
 constexpr int kMaxConsecutiveFailedLookups = 5;
 
+const char kBitrateEstimateExperiment[] = "WebRTC-ImprovedBitrateEstimate";
 const char kBweTrendlineFilterExperiment[] = "WebRTC-BweTrendlineFilter";
 const char kBweMedianSlopeFilterExperiment[] = "WebRTC-BweMedianSlopeFilter";
+
+bool BitrateEstimateExperimentIsEnabled() {
+  return webrtc::field_trial::IsEnabled(kBitrateEstimateExperiment);
+}
 
 bool TrendlineFilterExperimentIsEnabled() {
   std::string experiment_string =
@@ -148,9 +153,19 @@
       current_win_ms_(0),
       prev_time_ms_(-1),
       bitrate_estimate_(-1.0f),
-      bitrate_estimate_var_(50.0f) {}
+      bitrate_estimate_var_(50.0f),
+      old_estimator_(kBitrateWindowMs, 8000),
+      in_experiment_(BitrateEstimateExperimentIsEnabled()) {}
 
 void DelayBasedBwe::BitrateEstimator::Update(int64_t now_ms, int bytes) {
+  if (!in_experiment_) {
+    old_estimator_.Update(bytes, now_ms);
+    rtc::Optional<uint32_t> rate = old_estimator_.Rate(now_ms);
+    bitrate_estimate_ = -1.0f;
+    if (rate)
+      bitrate_estimate_ = *rate / 1000.0f;
+    return;
+  }
   int rate_window_ms = kRateWindowMs;
   // We use a larger window at the beginning to get a more stable sample that
   // we can use to initialize the estimate.