Add a silent audio sink to consume WebAudio data on silence detection.

content/renderer/media/renderer_webaudiodevice_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_RENDERER_WEBAUDIODEVICE_IMPL_H_
 #define CONTENT_RENDERER_MEDIA_RENDERER_WEBAUDIODEVICE_IMPL_H_
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/audio_renderer_sink.h"
 #include "third_party/WebKit/public/platform/WebAudioDevice.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace media {
 class AudioOutputDevice;
+class AudioTimestampHelper;
+class NullAudioSink;
 }
 
 namespace content {
 
 class RendererWebAudioDeviceImpl
     : public blink::WebAudioDevice,
       public media::AudioRendererSink::RenderCallback {
  public:
   RendererWebAudioDeviceImpl(const media::AudioParameters& params,
                              blink::WebAudioDevice::RenderCallback* callback,
                              int session_id);
   virtual ~RendererWebAudioDeviceImpl();
 
   // blink::WebAudioDevice implementation.
   virtual void start();
   virtual void stop();
   virtual double sampleRate();
 
   // AudioRendererSink::RenderCallback implementation.
   int Render(media::AudioBus* dest, int audio_delay_milliseconds) override;
 
   void OnRenderError() override;
 
  private:
+  // Helper method to start and stop the |null_audio_sink_|.
+  void StartNullAudioSink();
+  void StopNullAudioSink();
+
   const media::AudioParameters params_;
 
   // Weak reference to the callback into WebKit code.
   blink::WebAudioDevice::RenderCallback* const client_callback_;
 
   // To avoid the need for locking, ensure the control methods of the
   // blink::WebAudioDevice implementation are called on the same thread.
   base::ThreadChecker thread_checker_;
 
   // When non-NULL, we are started.  When NULL, we are stopped.
   scoped_refptr<media::AudioOutputDevice> output_device_;
 
   // ID to allow browser to select the correct input device for unified IO.
   int session_id_;
 
+  // Object to calculate the period of time in silence.
+  scoped_ptr<media::AudioTimestampHelper> audio_timestamp_helper_;
+
+  // TaskRunner to post callbacks to the render thread.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  // A fake audio sink object that consumes data when long period of silence
+  // audio is detected. This object lives on the render thread.
+  scoped_refptr<media::NullAudioSink> null_audio_sink_;
+
+  // Whether audio output is directed to |null_audio_sink_|.
+  bool is_using_null_audio_sink_;
+
+  // Weak pointer for posting callbacks.
+  base::WeakPtr<RendererWebAudioDeviceImpl> weak_this_;
+  // NOTE: Weak pointers must be invalidated before all other member variables.
+  base::WeakPtrFactory<RendererWebAudioDeviceImpl> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(RendererWebAudioDeviceImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_RENDERER_WEBAUDIODEVICE_IMPL_H_