Support REMB in combination with send-side BWE.

BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1581113006

Cr-Commit-Position: refs/heads/master@{#11322}
diff --git a/webrtc/modules/bitrate_controller/include/bitrate_controller.h b/webrtc/modules/bitrate_controller/include/bitrate_controller.h
index d1eca8e..a9c247a 100644
--- a/webrtc/modules/bitrate_controller/include/bitrate_controller.h
+++ b/webrtc/modules/bitrate_controller/include/bitrate_controller.h
@@ -57,6 +57,8 @@
   virtual void SetStartBitrate(int start_bitrate_bps) = 0;
   virtual void SetMinMaxBitrate(int min_bitrate_bps, int max_bitrate_bps) = 0;
 
+  virtual void UpdateDelayBasedEstimate(uint32_t bitrate_bps) = 0;
+
   virtual void SetEventLog(RtcEventLog* event_log) = 0;
 
   // Gets the available payload bandwidth in bits per second. Note that