Regression test for issue where Opus DTX status was being forgotten.

webrtc/modules/audio_coding/codecs/audio_encoder.cc

 /*
  *  Copyright (c) 2014 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 32 matching lines @@
 }
 
 bool AudioEncoder::SetFec(bool enable) {
   return !enable;
 }
 
 bool AudioEncoder::SetDtx(bool enable) {
   return !enable;
 }
 
+bool AudioEncoder::GetDtx() const {
+  return false;
+}
+
 bool AudioEncoder::SetApplication(Application application) {
   return false;
 }
 
 void AudioEncoder::SetMaxPlaybackRate(int frequency_hz) {}
 
 void AudioEncoder::SetProjectedPacketLossRate(double fraction) {}
 
 void AudioEncoder::SetTargetBitrate(int target_bps) {}
 
 rtc::ArrayView<std::unique_ptr<AudioEncoder>>
 AudioEncoder::ReclaimContainedEncoders() { return nullptr; }
 
 }  // namespace webrtc