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

modules/audio_coding/audio_network_adaptor/frame_length_controller.h

Index: modules/audio_coding/audio_network_adaptor/frame_length_controller.h
diff --git a/modules/audio_coding/audio_network_adaptor/frame_length_controller.h b/modules/audio_coding/audio_network_adaptor/frame_length_controller.h
index bbda77ed525d5a122b47e2063cb9e3595678ada0..c254b3dcf664cbf61b2aff62b24fc353bd1bd80c 100644
--- a/modules/audio_coding/audio_network_adaptor/frame_length_controller.h
+++ b/modules/audio_coding/audio_network_adaptor/frame_length_controller.h
@@ -35,6 +35,8 @@ class FrameLengthController final : public Controller {
            int min_encoder_bitrate_bps,
            float fl_increasing_packet_loss_fraction,
            float fl_decreasing_packet_loss_fraction,
+           int fl_increase_overhead_offset,
+           int fl_decrease_overhead_offset,
            std::map<FrameLengthChange, int> fl_changing_bandwidths_bps);
     Config(const Config& other);
     ~Config();
@@ -45,6 +47,10 @@ class FrameLengthController final : public Controller {
     float fl_increasing_packet_loss_fraction;
     // Uplink packet loss fraction below which frame length should decrease.
     float fl_decreasing_packet_loss_fraction;
+    // Offset to apply to overhead calculation when increasing frame length.
+    int fl_increase_overhead_offset;
+    // Offset to apply to overhead calculation when decreasing frame length.
+    int fl_decrease_overhead_offset;
     std::map<FrameLengthChange, int> fl_changing_bandwidths_bps;
   };
 
@@ -73,6 +79,10 @@ class FrameLengthController final : public Controller {
 
   rtc::Optional<size_t> overhead_bytes_per_packet_;
 
+  // True if the previous frame length decision was an increase, otherwise
+  // false.
+  bool prev_decision_increase_ = false;
+
   RTC_DISALLOW_COPY_AND_ASSIGN(FrameLengthController);
 };