Common: Add a NullAudioStream implementation

src/common/null_audio_stream.cpp

@@ -0,0 +1,20 @@
+#include "null_audio_stream.h"
+
+NullAudioStream::NullAudioStream() = default;
+
+NullAudioStream::~NullAudioStream() = default;
+
+bool NullAudioStream::OpenDevice()
+{
+  return true;
+}
+
+void NullAudioStream::PauseDevice(bool paused) {}
+
+void NullAudioStream::CloseDevice() {}
+
+void NullAudioStream::BufferAvailable()
+{
+  // drop any buffer as soon as they're available
+  DropBuffer();
+}