Revert of Move congestion controller processing to the pacer thread.

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index cbe3f2fe8accfe361301e64db8025ab3e4cf9f92..94b3d8c6da98bbaee3a070e8e9f2421044a758b9 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -327,19 +327,15 @@
 }
 
 int64_t CongestionController::TimeUntilNextProcess() {
-  return std::min({bitrate_controller_->TimeUntilNextProcess(),
-                   remote_bitrate_estimator_->TimeUntilNextProcess(),
-                   pacer_->TimeUntilNextProcess(),
-                   remote_estimator_proxy_.TimeUntilNextProcess()});
+  return std::min(bitrate_controller_->TimeUntilNextProcess(),
+                  remote_bitrate_estimator_->TimeUntilNextProcess());
 }
 
 void CongestionController::Process() {
   bitrate_controller_->Process();
   remote_bitrate_estimator_->Process();
+  probe_controller_->Process();
   MaybeTriggerOnNetworkChanged();
-  probe_controller_->Process();
-  pacer_->Process();
-  remote_estimator_proxy_.Process();
 }
 
 void CongestionController::MaybeTriggerOnNetworkChanged() {