Add WebThread in AudioDestination to support AudioWorkletThread

third_party/WebKit/Source/platform/audio/AudioDestination.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 25 matching lines @@
 #include "platform/wtf/Noncopyable.h"
 #include "platform/wtf/text/WTFString.h"
 #include "public/platform/WebAudioDevice.h"
 #include "public/platform/WebVector.h"
 
 namespace blink {
 
 class PushPullFIFO;
 class SecurityOrigin;
 class WebAudioLatencyHint;
+class WebThread;
 
 // The AudioDestination class is an audio sink interface between the media
 // renderer and the Blink's WebAudio module. It has a FIFO to adapt the
 // different processing block sizes of WebAudio renderer and actual hardware
 // audio callback.
 class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
   USING_FAST_MALLOC(AudioDestination);
   WTF_MAKE_NONCOPYABLE(AudioDestination);
 
  public:
@@ skipping 10 matching lines @@
       PassRefPtr<SecurityOrigin>);
 
   // The actual render function (WebAudioDevice::RenderCallback) isochronously
   // invoked by the media renderer.
   void Render(const WebVector<float*>& destination_data,
               size_t number_of_frames,
               double delay,
               double delay_timestamp,
               size_t prior_frames_skipped) override;
 
+  // The actual render request to the WebAudio destination node. This triggers
+  // the WebAudio rendering pipe line on the web thread.
+  void RequestRenderOnWebThread(size_t frames_requested,
+                                size_t frames_to_render,
+                                double delay,
+                                double delay_timestamp,
+                                size_t prior_frames_skipped);
+
   virtual void Start();
   virtual void Stop();
 
   size_t CallbackBufferSize() const { return callback_buffer_size_; }
   bool IsPlaying() { return is_playing_; }
 
   double SampleRate() const { return web_audio_device_->SampleRate(); }
 
   // Returns the audio buffer size in frames used by the underlying audio
   // hardware.
   int FramesPerBuffer() const { return web_audio_device_->FramesPerBuffer(); }
 
   // The information from the actual audio hardware. (via Platform::current)
   static float HardwareSampleRate();
   static unsigned long MaxChannelCount();
 
  private:
   std::unique_ptr<WebAudioDevice> web_audio_device_;
   unsigned number_of_output_channels_;

[o1ka, 2017/04/18 14:14:57]

Make it const? (I know it's an old code - we can make it better :) )

[hongchan, 2017/04/18 18:16:08]

Done.

   size_t callback_buffer_size_;
   bool is_playing_;
 
   // The render callback function of WebAudio engine. (i.e. DestinationNode)
   AudioIOCallback& callback_;

[o1ka, 2017/04/18 14:14:57]

Side comment: Is it WebKit style to use references for not-owned members with
guaranteed lifetime? Chromium style would be to receive (both in
AudioDestination::Create() and the constructor) and store a pointer, not a
reference.

[hongchan, 2017/04/18 18:16:08]

I haven't checked why it was written like this. If we have to change this, I
prefer to do that in a different CL after further investigation.

 
   // To pass the data from FIFO to the audio device callback.
   RefPtr<AudioBus> output_bus_;
 
   // To push the rendered result from WebAudio graph into the FIFO.
   RefPtr<AudioBus> render_bus_;
 
   // Resolves the buffer size mismatch between the WebAudio engine and
   // the callback function from the actual audio device.
   std::unique_ptr<PushPullFIFO> fifo_;
 
+  // WebThread for WebAudio rendering.
+  std::unique_ptr<WebThread> rendering_thread_;

[o1ka, 2017/04/18 14:14:57]

Could you group data members by thread they are accessed on, and add comments
about it: 
|render_bus_|, |frames_elapsed_| and |callback_| are accessed on
|rendering_thread_| only;
|output_bus_| is accessed on the device thread only?

[hongchan, 2017/04/18 18:16:08]

Done.

+
   size_t frames_elapsed_;
   AudioIOPosition output_position_;
   base::TimeTicks output_position_received_timestamp_;
 
   // Check if the buffer size chosen by the WebAudioDevice is too large.
   bool CheckBufferSize();
 
   size_t HardwareBufferSize();

[o1ka, 2017/04/18 14:14:57]

Chromium style is first methods, then members. Is WebKit different?

[hongchan, 2017/04/18 18:16:08]

Not that I know of. Eventually we're merging to Chromium style, so I will take
your suggestion here.

+
+  bool IsRenderingThread();
 };
 
 }  // namespace blink
 
 #endif  // AudioDestination_h