Add WebThread in AudioDestination to support AudioWorkletThread

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

Index: third_party/WebKit/Source/platform/audio/AudioDestination.h
diff --git a/third_party/WebKit/Source/platform/audio/AudioDestination.h b/third_party/WebKit/Source/platform/audio/AudioDestination.h
index 6bf30f33af2608473c36eb0b59c957efea71d48b..4677a1b63ef6bab40aab7f960556cd9f58e91abf 100644
--- a/third_party/WebKit/Source/platform/audio/AudioDestination.h
+++ b/third_party/WebKit/Source/platform/audio/AudioDestination.h
@@ -43,6 +43,7 @@ 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
@@ -73,6 +74,14 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
               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();
 
@@ -108,6 +117,9 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
   // 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_;
@@ -116,6 +128,8 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
   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