Smooth BWE and pass it to Audio Network Adaptor.

webrtc/common_audio/smoothing_filter.cc

 /*
  *  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.
  */
 
@@ skipping 41 matching lines @@
   filter_.Apply(static_cast<float>(last_sample_time_ms_ - now_ms), sample);
   last_sample_time_ms_ = now_ms;
 }
 
 rtc::Optional<float> SmoothingFilterImpl::GetAverage() const {
   float value = filter_.filtered();
   return value == rtc::ExpFilter::kValueUndefined ? rtc::Optional<float>()
                                                   : rtc::Optional<float>(value);
 }
 
+void SmoothingFilterImpl::SetTimeConstantMs(int time_constant_ms) {
+  time_constant_ms_ = time_constant_ms;
+  filter_.UpdateBase(exp(1.0f / time_constant_ms_));
+}
+
 }  // namespace webrtc