Tab Audio Capture: Browser-side connect/disconnect functionality.

content/browser/renderer_host/media/audio_renderer_host.h

Index: content/browser/renderer_host/media/audio_renderer_host.h
diff --git a/content/browser/renderer_host/media/audio_renderer_host.h b/content/browser/renderer_host/media/audio_renderer_host.h
index 44daef21f836cf0ee8da944de1d83fab60b04799..319db843a909e59728257bcd744f684601c3d2ef 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.h
+++ b/content/browser/renderer_host/media/audio_renderer_host.h
@@ -40,6 +40,7 @@
 #include <map>
 
 #include "base/gtest_prod_util.h"
+#include "base/lazy_instance.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process.h"
@@ -66,11 +67,29 @@ class CONTENT_EXPORT AudioRendererHost
     : public BrowserMessageFilter,
       public media::AudioOutputController::EventHandler {
  public:
+  // Interface to be implemented by audio mirroring destinations.  See
+  // comments for StartMirroring() and StopMirroring() below.
+  class MirroringDestination
+      : public base::RefCountedThreadSafe<MirroringDestination> {

[tommi (sloooow) - chröme, 2012/12/18 13:41:26]

Can we avoid reference counting here?  Instead use scoped_ptr and explicit
ownership passing where needed?

[miu, 2012/12/19 00:22:57]

With the breaking-out of the mirroring functionality, I was able to remove the
ref-counting on this interface.  :-)

+   public:
+    // Create a consumer of audio data in the format specified by |params|, and
+    // connect it as an input to mirroring.  When Close() is called, the input
+    // is disconnected and the object becomes invalid.
+    virtual media::AudioOutputStream* AddInput(
+        const media::AudioParameters& params) = 0;
+
+   protected:
+    friend class base::RefCountedThreadSafe<MirroringDestination>;
+    virtual ~MirroringDestination();
+  };
+
   // Called from UI thread from the owner of this object.
-  AudioRendererHost(media::AudioManager* audio_manager,
+  AudioRendererHost(int render_process_id,
+                    media::AudioManager* audio_manager,
                     MediaObserver* media_observer);
 
   // BrowserMessageFilter implementation.
+  virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
   virtual void OnChannelClosing() OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
@@ -83,6 +102,18 @@ class CONTENT_EXPORT AudioRendererHost
   virtual void OnError(media::AudioOutputController* controller,
                        int error_code) OVERRIDE;
 
+  // Start/stop mirroring all audio output streams associated with
+  // |render_process_id| + |render_view_id| to |destination|.  Any call to
+  // StartMirroring() must be paired with a later call to StopMirroring() since
+  // a reference is held on the MirroringDestination while the mirroring session
+  // is active.
+  static void StartMirroring(

[DaleCurtis, 2012/12/17 20:00:47]

I worry somewhat about what seems to be the bolting on of Mirroring
functionality via static methods here. Would it make more sense for
AudioRendererHost to access a lazy-instance TabMirroring() object that holds all
this functionality?

Having all these static methods tells me this functionality could probably live
in a separate helper class for clarity.

[tommi (sloooow) - chröme, 2012/12/18 13:41:26]

+1.  Maybe a Mirror object of sorts per render view with Start and Stop methods.

[miu, 2012/12/19 00:22:57]

Yeah, now that you guys have pointed it out, I agree too.  So, I broke the
functionality out into a separate AudioMirroringManager.

AudioRendererHost will tell AudioMirroringManager about all the streams as they
are created and closed, and provide a simple object that implements the
AudioMirroringManager::Diverter interface.  Then, WebContentsAudioInputStream
(in a later CL) will call StartMirroring() and StopMirroring().  The unit tests
(in audio_mirroring_manager_unittest.cc) should make everything obvious.

PTAL.

+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+  static void StopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+
  private:
   friend class AudioRendererHostTest;
   friend class BrowserThread;
@@ -93,6 +124,8 @@ class CONTENT_EXPORT AudioRendererHost
 
   struct AudioEntry;
   typedef std::map<int, AudioEntry*> AudioEntryMap;
+  typedef std::map<int, scoped_refptr<MirroringDestination> > MirrorSessionMap;
+  typedef std::map<int, AudioRendererHost*> ActiveHostMap;
 
   virtual ~AudioRendererHost();
 
@@ -164,12 +197,35 @@ class CONTENT_EXPORT AudioRendererHost
 
   media::AudioOutputController* LookupControllerByIdForTesting(int stream_id);
 
+  // Global look-up for the AudioRendererHost instance owned by the
+  // RenderProcessHost specified by |render_process_id|.
+  static AudioRendererHost* FromRenderProcessID(int render_process_id);
+
+  // Implementations for StartMirroring() and StopMirroring() that are run on
+  // the IO BrowserThread.
+  static void DoStartMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+  static void DoStopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+
+  // ID of the RenderProcessHost that owns this instance.
+  const int render_process_id_;
+
   // A map of stream IDs to audio sources.
   AudioEntryMap audio_entries_;
 
+  // A map of render view IDs to the destination for active mirroring sessions.
+  MirrorSessionMap mirror_sessions_;
+
   media::AudioManager* audio_manager_;
   MediaObserver* media_observer_;
 
+  // Global look-up map for currently-active (i.e., IPC channel is open)
+  // AudioRendererHosts.
+  static base::LazyInstance<ActiveHostMap>::Leaky g_host_map_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioRendererHost);
 };