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

webrtc/modules/audio_coding/audio_network_adaptor/include/audio_network_adaptor_config.h

 /*
  *  Copyright (c) 2017 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 13 matching lines @@
   // Note: This is what we tell the encoder. It doesn't have to reflect
   // the actual NetworkMetrics; it's subject to our decision.
   rtc::Optional<float> uplink_packet_loss_fraction;
   rtc::Optional<bool> enable_fec;
   rtc::Optional<bool> enable_dtx;
 
   // Some encoders can encode fewer channels than the actual input to make
   // better use of the bandwidth. |num_channels| sets the number of channels
   // to encode.
   rtc::Optional<size_t> num_channels;
+
+  // This is true if the last frame length change was an increase, and otherwise
+  // false. Note that the default value of this variable may need to be updated

[ossu, 2017/09/14 12:16:14]

"Note that the default value of this variable may need to be updated if the
default frame length is increased."

Why?

[ivoc, 2017/09/14 13:03:39]

I guess this is a bit arbitrary and probably doesn't make a big difference, so I
decided to remove this comment. 

My thinking was that we're currently initializing the frame length to the
smallest supported value (20 ms), so it would be weird if we initialize this
variable to say that the last operation was an increase. But in the future, if
the initial frame length would be the maximum value (I guess that's pretty
unlikely anyway), then this current default wouldn't make sense anymore.

+  // if the default frame length is increased.
+  bool last_fl_change_increase = false;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_INCLUDE_AUDIO_NETWORK_ADAPTOR_CONFIG_H_