NetEq: Add a VoidAudioSink tool

webrtc/modules/audio_coding/neteq/tools/audio_sink.h

 /*
  *  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 38 matching lines @@
 
   bool WriteArray(const int16_t* audio, size_t num_samples) override;
 
  private:
   AudioSink* left_sink_;
   AudioSink* right_sink_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioSinkFork);
 };
 
+// An AudioSink implementation that does nothing.
+class VoidAudioSink : public AudioSink {
+ public:
+  VoidAudioSink() = default;
+  bool WriteArray(const int16_t* audio, size_t num_samples) override;
+
+ private:
+  RTC_DISALLOW_COPY_AND_ASSIGN(VoidAudioSink);
+};
+
 }  // namespace test
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_TOOLS_AUDIO_SINK_H_