NetEq: Add a VoidAudioSink tool

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

Index: webrtc/modules/audio_coding/neteq/tools/audio_sink.cc
diff --git a/webrtc/modules/audio_coding/neteq/tools/audio_sink.cc b/webrtc/modules/audio_coding/neteq/tools/audio_sink.cc
index fb848bdbd9b53e62af0c2a8cfb7fb3668a8e75c5..665dc412bd32d60def450f157689eef3554d8abd 100644
--- a/webrtc/modules/audio_coding/neteq/tools/audio_sink.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/audio_sink.cc
@@ -17,5 +17,10 @@ bool AudioSinkFork::WriteArray(const int16_t* audio, size_t num_samples) {
   return left_sink_->WriteArray(audio, num_samples) &&
          right_sink_->WriteArray(audio, num_samples);
 }
+
+bool VoidAudioSink::WriteArray(const int16_t* audio, size_t num_samples) {
+  return true;
+}
+
 }  // namespace test
 }  // namespace webrtc