NetEq: Add a VoidAudioSink tool

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

Index: webrtc/modules/audio_coding/neteq/tools/audio_sink.h
diff --git a/webrtc/modules/audio_coding/neteq/tools/audio_sink.h b/webrtc/modules/audio_coding/neteq/tools/audio_sink.h
index 8a5479ef267566fa07543bfd36496f2038e30ab3..71b387a89a49c5f52ec335ceea84a7d243c5e003 100644
--- a/webrtc/modules/audio_coding/neteq/tools/audio_sink.h
+++ b/webrtc/modules/audio_coding/neteq/tools/audio_sink.h
@@ -56,6 +56,16 @@ class AudioSinkFork : public AudioSink {
   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_