Added configurable offsets to the per-packet overhead in ANA.

modules/audio_coding/audio_network_adaptor/bitrate_controller.h

 /*
  *  Copyright (c) 2016 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.
  */
 
 #ifndef MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_BITRATE_CONTROLLER_H_
 #define MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_BITRATE_CONTROLLER_H_
 
 #include "modules/audio_coding/audio_network_adaptor/controller.h"
 #include "rtc_base/constructormagic.h"
 
 namespace webrtc {
 namespace audio_network_adaptor {
 
 class BitrateController final : public Controller {
  public:
   struct Config {
-    Config(int initial_bitrate_bps, int initial_frame_length_ms);
+    Config(int initial_bitrate_bps,
+           int initial_frame_length_ms,
+           int fl_increase_overhead_offset,
+           int fl_decrease_overhead_offset);
     ~Config();
     int initial_bitrate_bps;
     int initial_frame_length_ms;
+    int fl_increase_overhead_offset;
+    int fl_decrease_overhead_offset;
   };
 
   explicit BitrateController(const Config& config);
 
   ~BitrateController() override;
 
   void UpdateNetworkMetrics(const NetworkMetrics& network_metrics) override;
 
   void MakeDecision(AudioEncoderRuntimeConfig* config) override;
 
  private:
   const Config config_;
   int bitrate_bps_;
   int frame_length_ms_;
   rtc::Optional<int> target_audio_bitrate_bps_;
   rtc::Optional<size_t> overhead_bytes_per_packet_;
   RTC_DISALLOW_COPY_AND_ASSIGN(BitrateController);
 };
 
 }  // namespace audio_network_adaptor
 }  // namespace webrtc
 
 #endif  // MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_BITRATE_CONTROLLER_H_