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

webrtc/modules/audio_coding/include/audio_coding_module.h

 /*
  *  Copyright (c) 2012 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 232 matching lines @@
   };
 
   // |modifier| is called exactly once with one argument: a pointer to the
   // unique_ptr that holds the current encoder (which is null if there is no
   // current encoder). For the duration of the call, |modifier| has exclusive
   // access to the unique_ptr; it may call the encoder, steal the encoder and
   // replace it with another encoder or with nullptr, etc.
   virtual void ModifyEncoder(
       FunctionView<void(std::unique_ptr<AudioEncoder>*)> modifier) = 0;
 
+  // |modifier| is called exactly once with one argument: a const pointer to the
+  // current encoder (which is null if there is no current encoder).
+  virtual void QueryEncoder(FunctionView<void(AudioEncoder const*)> query) = 0;
+
   // Utility method for simply replacing the existing encoder with a new one.
   void SetEncoder(std::unique_ptr<AudioEncoder> new_encoder) {
     ModifyEncoder([&](std::unique_ptr<AudioEncoder>* encoder) {
       *encoder = std::move(new_encoder);
     });
   }
 
   ///////////////////////////////////////////////////////////////////////////
   // int32_t SendCodec()
   // Get parameters for the codec currently registered as send codec.
@@ skipping 549 matching lines @@
   virtual std::vector<uint16_t> GetNackList(
       int64_t round_trip_time_ms) const = 0;
 
   virtual void GetDecodingCallStatistics(
       AudioDecodingCallStats* call_stats) const = 0;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_INCLUDE_AUDIO_CODING_MODULE_H_