Experimental: Unmute Audio During Tab Sourced Desktop Share

media/audio/virtual_audio_output_stream.h

Index: media/audio/virtual_audio_output_stream.h
diff --git a/media/audio/virtual_audio_output_stream.h b/media/audio/virtual_audio_output_stream.h
index 84b929c73cd2b6291dc234a5964a4c7cd798b1b7..777332ecbf08e6e850f50af2cc54a69a574b938c 100644
--- a/media/audio/virtual_audio_output_stream.h
+++ b/media/audio/virtual_audio_output_stream.h
@@ -11,6 +11,7 @@
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/audio_converter.h"
+#include "media/base/audio_shifter.h"
 
 namespace media {
 
@@ -66,6 +67,45 @@ class MEDIA_EXPORT VirtualAudioOutputStream
   DISALLOW_COPY_AND_ASSIGN(VirtualAudioOutputStream);
 };
 
+class MEDIA_EXPORT AudioPushSink : public AudioInputStream::AudioInputCallback {
+ public:
+  virtual void Start() = 0;
+  virtual void Stop() = 0;
+  virtual void Close() = 0;
+};
+
+class MEDIA_EXPORT LoopbackSink : public AudioPushSink,
+                                  public AudioConverter::InputCallback {
+ public:
+  typedef base::Callback<void(LoopbackSink* sink)> AfterCloseCallback;
+
+  LoopbackSink(AudioParameters param,
+               VirtualAudioInputStream* target,
+               AfterCloseCallback callback);
+  ~LoopbackSink() override;
+
+  // AudioPushSink
+  void Start() override;
+  void Stop() override;
+  void Close() override;
+  void OnData(AudioInputStream* stream,
+              const AudioBus* source,
+              uint32_t hardware_delay_bytes,
+              double volume) override;
+  void OnError(AudioInputStream* stream) override;
+
+  // AudioConverter::InputCallback
+  double ProvideInput(AudioBus* audio_bus,
+                      base::TimeDelta buffer_delay) override;
+
+ private:
+  bool started_;
+  AudioParameters params_;
+  VirtualAudioInputStream* target_;
+  std::unique_ptr<AudioShifter> shifter_;
+  AfterCloseCallback after_close_callback_;
+};
+
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_VIRTUAL_AUDIO_OUTPUT_STREAM_H_