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

modules/audio_coding/audio_network_adaptor/config.proto

 syntax = "proto2";
 option optimize_for = LITE_RUNTIME;
 option java_package = "org.webrtc.AudioNetworkAdaptor";
 option java_outer_classname = "Config";
 package webrtc.audio_network_adaptor.config;
 
 message FecController {
   message Threshold {
     // Threshold defines a curve in the bandwidth/packet-loss domain. The
     // curve is characterized by the two conjunction points: A and B.
@@ skipping 74 matching lines @@
   optional int32 fl_20ms_to_60ms_bandwidth_bps = 3;
 
   // Uplink bandwidth above which frame length should switch from 60ms to 20ms.
   optional int32 fl_60ms_to_20ms_bandwidth_bps = 4;
 
   // Uplink bandwidth below which frame length can switch from 60ms to 120ms.
   optional int32 fl_60ms_to_120ms_bandwidth_bps = 5;
 
   // Uplink bandwidth above which frame length should switch from 120ms to 60ms.
   optional int32 fl_120ms_to_60ms_bandwidth_bps = 6;
+
+  // Offset to apply to the per-packet overhead when increasing frame length.
+  optional int32 fl_increase_overhead_offset = 7;
+
+  // Offset to apply to the per-packet overhead when decreasing frame length.
+  optional int32 fl_decrease_overhead_offset = 8;
 }
 
 message ChannelController {
   // Uplink bandwidth above which the number of encoded channels should switch
   // from 1 to 2.
   optional int32 channel_1_to_2_bandwidth_bps = 1;
 
   // Uplink bandwidth below which the number of encoded channels should switch
   // from 2 to 1.
   optional int32 channel_2_to_1_bandwidth_bps = 2;
 }
 
 message DtxController {
   // Uplink bandwidth below which DTX should be switched on.
   optional int32 dtx_enabling_bandwidth_bps = 1;
 
   // Uplink bandwidth above which DTX should be switched off.
   optional int32 dtx_disabling_bandwidth_bps = 2;
 }
 
-message BitrateController {}
+message BitrateController {
+  // Offset to apply to per-packet overhead when the frame length is increased.
+  optional int32 fl_increase_overhead_offset = 1;
+  // Offset to apply to per-packet overhead when the frame length is decreased.
+  optional int32 fl_decrease_overhead_offset = 2;
+}
 
 message Controller {
   message ScoringPoint {
     // |ScoringPoint| is a subspace of network condition. It is used for
     // comparing the significance of controllers.
     optional int32 uplink_bandwidth_bps = 1;
     optional float uplink_packet_loss_fraction = 2;
   }
 
   // The distance from |scoring_point| to a given network condition defines
@@ skipping 18 matching lines @@
   repeated Controller controllers = 1;
 
   // Least time since last reordering for a new reordering to be made.
   optional int32 min_reordering_time_ms = 2;
 
   // Least squared distance from last scoring point for a new reordering to be
   // made.
   optional float min_reordering_squared_distance = 3;
 }