Set the start bitrate to the delay-based BWE.

webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h

Index: webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
diff --git a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
index ddfa667a87f629ffd9d978196c73c51ce7f2c700..b3c5928e054af3ab1657ff84258214a234a45f73 100644
--- a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
+++ b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h
@@ -24,11 +24,12 @@ namespace webrtc {
 class AimdRateControl {
  public:
   AimdRateControl();
-  virtual ~AimdRateControl() {}
+  virtual ~AimdRateControl();
 
   // Returns true if there is a valid estimate of the incoming bitrate, false
   // otherwise.
   bool ValidEstimate() const;
+  void SetStartBitrate(int start_bitrate_bps);
   void SetMinBitrate(int min_bitrate_bps);
   int64_t GetFeedbackInterval() const;
   // Returns true if the bitrate estimate hasn't been changed for more than