Set the start bitrate to the delay-based BWE.

webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc

Index: webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
index e0c9ccd3ba4ac1f44d77c4b5d01b363e7bac05fe..fdee6df86762160adb9a9122668b85e4b94694c7 100644
--- a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
+++ b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
@@ -43,6 +43,13 @@ AimdRateControl::AimdRateControl()
       rtt_(kDefaultRttMs),
       in_experiment_(!AdaptiveThresholdExperimentIsDisabled()) {}
 
+AimdRateControl::~AimdRateControl() {}
+
+void AimdRateControl::SetStartBitrate(int start_bitrate_bps) {
+  current_bitrate_bps_ = start_bitrate_bps;
+  bitrate_is_initialized_ = true;
+}
+
 void AimdRateControl::SetMinBitrate(int min_bitrate_bps) {
   min_configured_bitrate_bps_ = min_bitrate_bps;
   current_bitrate_bps_ = std::max<int>(min_bitrate_bps, current_bitrate_bps_);