Second layer of mixing for audio elements.

media/audio/virtual_audio_input_stream.cc

Index: media/audio/virtual_audio_input_stream.cc
diff --git a/media/audio/virtual_audio_input_stream.cc b/media/audio/virtual_audio_input_stream.cc
index e586ac88618872d9790c0e3e1e30bb3a6ed5e408..6f35becf54f2512fa150822607f05d8c12fc6489 100644
--- a/media/audio/virtual_audio_input_stream.cc
+++ b/media/audio/virtual_audio_input_stream.cc
@@ -10,43 +10,10 @@
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
 #include "media/audio/virtual_audio_output_stream.h"
+#include "media/base/loopback_audio_converter.h"
 
 namespace media {
 
-// LoopbackAudioConverter works similar to AudioConverter and converts input
-// streams to different audio parameters. Then, the LoopbackAudioConverter can
-// be used as an input to another AudioConverter. This allows us to
-// use converted audio from AudioOutputStreams as input to an AudioConverter.
-// For example, this allows converting multiple streams into a common format and
-// using the converted audio as input to another AudioConverter (i.e. a mixer).
-class LoopbackAudioConverter : public AudioConverter::InputCallback {
- public:
-  LoopbackAudioConverter(const AudioParameters& input_params,
-                         const AudioParameters& output_params)
-      : audio_converter_(input_params, output_params, false) {}
-
-  ~LoopbackAudioConverter() override {}
-
-  void AddInput(AudioConverter::InputCallback* input) {
-    audio_converter_.AddInput(input);
-  }
-
-  void RemoveInput(AudioConverter::InputCallback* input) {
-    audio_converter_.RemoveInput(input);
-  }
-
- private:
-  double ProvideInput(AudioBus* audio_bus,
-                      base::TimeDelta buffer_delay) override {
-    audio_converter_.ConvertWithDelay(buffer_delay, audio_bus);
-    return 1.0;
-  }
-
-  AudioConverter audio_converter_;
-
-  DISALLOW_COPY_AND_ASSIGN(LoopbackAudioConverter);
-};
-
 VirtualAudioInputStream::VirtualAudioInputStream(
     const AudioParameters& params,
     const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner,
@@ -109,8 +76,8 @@ void VirtualAudioInputStream::AddOutputStream(
   AudioConvertersMap::iterator converter = converters_.find(output_params);
   if (converter == converters_.end()) {
     std::pair<AudioConvertersMap::iterator, bool> result = converters_.insert(
-        std::make_pair(output_params,
-                       new LoopbackAudioConverter(output_params, params_)));
+        std::make_pair(output_params, new LoopbackAudioConverter(
+                                          output_params, params_, false)));
     converter = result.first;
 
     // Add to main mixer if we just added a new AudioTransform.