Do not update OnReceivedRtcpReceiverReport if report block list is empty (and rtt zero).

webrtc/modules/bitrate_controller/bitrate_controller_impl.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  *
  */
@@ skipping 20 matching lines @@
   virtual ~RtcpBandwidthObserverImpl() {
   }
   // Received RTCP REMB or TMMBR.
   void OnReceivedEstimatedBitrate(uint32_t bitrate) override {
     owner_->OnReceiverEstimatedBitrate(bitrate);
   }
   // Received RTCP receiver block.
   void OnReceivedRtcpReceiverReport(const ReportBlockList& report_blocks,
                                     int64_t rtt,
                                     int64_t now_ms) override {
+    if (report_blocks.empty())
+      return;
+
     int fraction_lost_aggregate = 0;
     int total_number_of_packets = 0;
 
     // Compute the a weighted average of the fraction loss from all report
     // blocks.
     for (const RTCPReportBlock& report_block : report_blocks) {
       std::map<uint32_t, uint32_t>::iterator seq_num_it =
           ssrc_to_last_received_extended_high_seq_num_.find(
               report_block.sourceSSRC);
 
@@ skipping 232 matching lines @@
   bandwidth_estimation_.CurrentEstimate(&bitrate, &fraction_loss, &rtt);
   if (bitrate > 0) {
     bitrate = bitrate - std::min<int>(bitrate, reserved_bitrate_bps_);
     bitrate = std::max(bitrate, bandwidth_estimation_.GetMinBitrate());
     *bandwidth = bitrate;
     return true;
   }
   return false;
 }
 }  // namespace webrtc