Add AudioStreamRegistry. Move stream counting logic

content/browser/renderer_host/media/audio_output_delegate.h

Index: content/browser/renderer_host/media/audio_output_delegate.h
diff --git a/content/browser/renderer_host/media/audio_output_delegate.h b/content/browser/renderer_host/media/audio_output_delegate.h
index 2744295acb9a810d9bd9cc060947e211fa3d5a0e..b68b9ffca0fd95014be7a87dfb474c4099225d34 100644
--- a/content/browser/renderer_host/media/audio_output_delegate.h
+++ b/content/browser/renderer_host/media/audio_output_delegate.h
@@ -10,6 +10,7 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "content/browser/renderer_host/media/audio_stream_registry.h"
 #include "content/common/content_export.h"
 #include "media/audio/audio_output_controller.h"
 
@@ -34,7 +35,8 @@ namespace content {
 // This class, except for the AudioOutputDelegate::EventHandler implementation,
 // is operated on the IO thread.
 class CONTENT_EXPORT AudioOutputDelegate
-    : public media::AudioOutputController::EventHandler {
+    : public media::AudioOutputController::EventHandler,
+      public AudioStreamRegistry::Stream {
  public:
   class CONTENT_EXPORT EventHandler {
    public:
@@ -42,9 +44,6 @@ class CONTENT_EXPORT AudioOutputDelegate
 
     // All these methods are called on the IO thread.
 
-    // Called when the state changes between playing and not playing.
-    virtual void OnStreamStateChanged(bool playing) = 0;
-
     // Called when construction is finished and the stream is ready for
     // playout.
     virtual void OnStreamCreated(int stream_id,
@@ -71,6 +70,7 @@ class CONTENT_EXPORT AudioOutputDelegate
   // The AudioOutputDelegate might issue callbacks until the UniquePtr
   // destructor finishes, so calling |handler| must be valid until then.
   static UniquePtr Create(EventHandler* handler,
+                          AudioStreamRegistry* stream_registry,
                           media::AudioManager* audio_manager,
                           std::unique_ptr<media::AudioLog> audio_log,
                           AudioMirroringManager* mirroring_manager,
@@ -80,6 +80,7 @@ class CONTENT_EXPORT AudioOutputDelegate
                           int render_process_id,
                           const media::AudioParameters& params,
                           const std::string& output_device_id);
+
   ~AudioOutputDelegate() override;
 
   // TODO(maxmorin): Remove this when crbug.com/647185 is closed.
@@ -95,6 +96,11 @@ class CONTENT_EXPORT AudioOutputDelegate
 
   int stream_id() const { return stream_id_; }
 
+#if BUILDFLAG(ENABLE_WEBRTC)
+  void EnableDebugRecording(const base::FilePath& base_file_name) override;

[o1ka, 2016/12/22 10:46:51]

Oh, I just realized. AusioStreamRegistry will live in the audio process, right?
Enable/Disable debug recording per stream should be a process-local operation.
And AuiodOutputDelegate is basically our representation of IPC. So, it looks
like AudioOutputController is one who should be AusioStreamRegistry::Stream.

[Max Morin, 2017/01/09 15:34:23]

I think AudioStreamRegistry will live in the browser process. The stream
counting is needed for RPH to know if the renderer should be backgrounded, and I
don't think we want the mojo jump every time we check that. Possibly,
AudioStreamRegistry just gets updates to a HasAudio bit from the audio process.
The stream counting (for stats) can be done completely in the browser process.
Finally, debug recording is a bit tricky (since we'll need to supply file
descriptors to the audio process). We might have the stream factories in the
audio process return two objects: an (Input/Output)Stream which the browser
sends to renderer and another interface to the stream which the browser keeps
with (Enable/Disable)DebugRecording (and maybe something else).

It doesn't matter much if AudioOutputDelegate or AudioOutputController is the
Stream, I picked AudioOutputDelegate because it lives on the IO thread, so we
have an easier time with thread management like this.

[o1ka, 2017/01/10 11:47:40]

Ah ok, sounds good. Stream interfaces need to be figured, not sure how well it
will look in Mojo world.

+  void DisableDebugRecording() override;
+#endif  // BUILDFLAG(ENABLE_WEBRTC)
+
   // Stream control:
   void OnPlayStream();
   void OnPauseStream();
@@ -109,6 +115,7 @@ class CONTENT_EXPORT AudioOutputDelegate
 
  private:
   AudioOutputDelegate(EventHandler* handler,
+                      AudioStreamRegistry* stream_registry,
                       media::AudioManager* audio_manager,
                       std::unique_ptr<media::AudioLog> audio_log,
                       int stream_id,
@@ -124,6 +131,7 @@ class CONTENT_EXPORT AudioOutputDelegate
   // |handler_| is null if we are in the process of destruction. In this case,
   // we will ignore events from |controller_|.
   EventHandler* handler_;
+  AudioStreamRegistry* const stream_registry_;
   std::unique_ptr<media::AudioLog> const audio_log_;
   std::unique_ptr<AudioSyncReader> reader_;
   scoped_refptr<media::AudioOutputController> controller_;