fallback to null sink in WebAudioSourceProvider::Initialize() + UMA stats for device status

media/blink/webaudiosourceprovider_impl.h

 // Copyright 2013 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 MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 #define MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
 #include "third_party/WebKit/public/platform/WebAudioSourceProvider.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 
 namespace blink {
 class WebAudioSourceProviderClient;
 }
 
 namespace media {
+class MediaLog;
 
 // WebAudioSourceProviderImpl is either one of two things (but not both):
 // - a connection between a RestartableAudioRendererSink (the |sink_|) passed in
 //   constructor and an AudioRendererSink::RenderCallback passed on Initialize()
 //   by means of an internal AudioRendererSink::RenderCallback.
 // - a connection between the said AudioRendererSink::RenderCallback and a
 //   blink::WebAudioSourceProviderClient passed via setClient() (the |client_|),
 //   again using the internal AudioRendererSink::RenderCallback. Blink calls
 //   provideInput() periodically to fetch the appropriate data.
 //
 // In either case, the internal RenderCallback allows for delivering a copy of
 // the data if a listener is configured. WASPImpl is also a
 // RestartableAudioRendererSink itself in order to be controlled (Play(),
 // Pause() etc).
 //
 // All calls are protected by a lock.
 class MEDIA_BLINK_EXPORT WebAudioSourceProviderImpl
     : NON_EXPORTED_BASE(public blink::WebAudioSourceProvider),
       NON_EXPORTED_BASE(public SwitchableAudioRendererSink) {
  public:
   using CopyAudioCB = base::Callback<void(std::unique_ptr<AudioBus>,
                                           uint32_t frames_delayed,
                                           int sample_rate)>;
 
-  explicit WebAudioSourceProviderImpl(
-      const scoped_refptr<SwitchableAudioRendererSink>& sink);
+  WebAudioSourceProviderImpl(scoped_refptr<SwitchableAudioRendererSink> sink,
+                             scoped_refptr<MediaLog> media_log);
 
   // blink::WebAudioSourceProvider implementation.
   void setClient(blink::WebAudioSourceProviderClient* client) override;
   void provideInput(const blink::WebVector<float*>& audio_data,
                     size_t number_of_frames) override;
 
   // RestartableAudioRendererSink implementation.
   void Initialize(const AudioParameters& params,
                   RenderCallback* renderer) override;
   void Start() override;
   void Stop() override;
   void Play() override;
   void Pause() override;
   bool SetVolume(double volume) override;
   OutputDeviceInfo GetOutputDeviceInfo() override;
   bool CurrentThreadIsRenderingThread() override;
   void SwitchOutputDevice(const std::string& device_id,
                           const url::Origin& security_origin,
                           const OutputDeviceStatusCB& callback) override;
 
   // These methods allow a client to get a copy of the rendered audio.
   void SetCopyAudioCallback(const CopyAudioCB& callback);
   void ClearCopyAudioCallback();
 
   int RenderForTesting(AudioBus* audio_bus);
 
+ protected:
+  virtual scoped_refptr<SwitchableAudioRendererSink> CreateFallbackSink();
+  ~WebAudioSourceProviderImpl() override;
+
  private:
   friend class WebAudioSourceProviderImplTest;
-  ~WebAudioSourceProviderImpl() override;
 
   // Calls setFormat() on |client_| from the Blink renderer thread.
   void OnSetFormat();
 
   // Used to keep the volume across reconfigurations.
   double volume_;
 
   // Tracks the current playback state.
   enum PlaybackState { kStopped, kStarted, kPlaying };
   PlaybackState state_;
 
   // Closure that calls OnSetFormat() on |client_| on the renderer thread.
   base::Closure set_format_cb_;
   // When set via setClient() it overrides |sink_| for consuming audio.
   blink::WebAudioSourceProviderClient* client_;
 
   // Where audio ends up unless overridden by |client_|.
   base::Lock sink_lock_;
-  const scoped_refptr<SwitchableAudioRendererSink> sink_;
+  scoped_refptr<SwitchableAudioRendererSink> sink_;
   std::unique_ptr<AudioBus> bus_wrapper_;
 
   // An inner class acting as a T filter where actual data can be tapped.
   class TeeFilter;
   const std::unique_ptr<TeeFilter> tee_filter_;
 
+  const scoped_refptr<MediaLog> media_log_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<WebAudioSourceProviderImpl> weak_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebAudioSourceProviderImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBAUDIOSOURCEPROVIDER_IMPL_H_