MediaStream audio object graph untangling and clean-ups.

content/renderer/media/webaudio_capturer_source.h

Index: content/renderer/media/webaudio_capturer_source.h
diff --git a/content/renderer/media/webaudio_capturer_source.h b/content/renderer/media/webaudio_capturer_source.h
index b0ee262ccd7c3c06135b9252b3b394db8c0dc7dd..e426994b27415f60060ad2b3c1c792efd60b6b5d 100644
--- a/content/renderer/media/webaudio_capturer_source.h
+++ b/content/renderer/media/webaudio_capturer_source.h
@@ -8,7 +8,6 @@
 #include <stddef.h>
 
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 #include "media/audio/audio_parameters.h"
@@ -29,12 +28,11 @@ class WebRtcLocalAudioTrack;
 //    (channels, and sample-rate).
 // 2. consumeAudio() is called periodically by WebKit which dispatches the
 //    audio stream to the WebRtcLocalAudioTrack::Capture() method.
-class WebAudioCapturerSource
-    :  public base::RefCountedThreadSafe<WebAudioCapturerSource>,
-       public blink::WebAudioDestinationConsumer {
+class WebAudioCapturerSource : public blink::WebAudioDestinationConsumer {
  public:
-  explicit WebAudioCapturerSource(
-      const blink::WebMediaStreamSource& blink_source);
+  explicit WebAudioCapturerSource(blink::WebMediaStreamSource* blink_source);
+
+  ~WebAudioCapturerSource() override;
 
   // WebAudioDestinationConsumer implementation.
   // setFormat() is called early on, so that we can configure the audio track.
@@ -45,29 +43,21 @@ class WebAudioCapturerSource
                     size_t number_of_frames) override;
 
   // Called when the WebAudioCapturerSource is hooking to a media audio track.
-  // |track| is the sink of the data flow. |source_provider| is the source of
-  // the data flow where stream information like delay, volume, key_pressed,
-  // is stored.
+  // |track| is the sink of the data flow and must remain alive until Stop() is
+  // called.
   void Start(WebRtcLocalAudioTrack* track);
 
   // Called when the media audio track is stopping.
   void Stop();
 
- protected:
-  friend class base::RefCountedThreadSafe<WebAudioCapturerSource>;
-  ~WebAudioCapturerSource() override;
-
  private:
-  // Removes this object from a blink::WebMediaStreamSource with which it
-  // might be registered. The goal is to avoid dangling pointers.
-  void removeFromBlinkSource();
+  // Deregisters this object from its blink::WebMediaStreamSource.
+  void DeregisterFromBlinkSource();
 
   // Used to DCHECK that some methods are called on the correct thread.
   base::ThreadChecker thread_checker_;
 
   // The audio track this WebAudioCapturerSource is feeding data to.
-  // WebRtcLocalAudioTrack is reference counted, and owning this object.
-  // To avoid circular reference, a raw pointer is kept here.
   WebRtcLocalAudioTrack* track_;

[mcasas, 2016/02/26 01:28:19]

Shouldn't this guy be a WeakPtr?

[miu, 2016/02/27 03:46:36]

No.  It must remain alive until Stop() is called (which sets it to nullptr). 
See comment for Start().

That said, this will go away in an upcoming change, where the relationship
between sources and tracks is made consistent for all sources and tracks.  ;-)

 
   media::AudioParameters params_;