MediaStream audio object graph untangling and clean-ups.

content/renderer/media/webaudio_capturer_source.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_WEBAUDIO_CAPTURER_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_WEBAUDIO_CAPTURER_SOURCE_H_
 
 #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 "base/time/time.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/audio_bus.h"
 #include "media/base/audio_capturer_source.h"
 #include "media/base/audio_push_fifo.h"
 #include "third_party/WebKit/public/platform/WebAudioDestinationConsumer.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 
 namespace content {
 
 class WebRtcLocalAudioTrack;
 
 // WebAudioCapturerSource is the missing link between
 // WebAudio's MediaStreamAudioDestinationNode and WebRtcLocalAudioTrack.
 //
 // 1. WebKit calls the setFormat() method setting up the basic stream format
 //    (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.
   void setFormat(size_t number_of_channels, float sample_rate) override;
   // MediaStreamAudioDestinationNode periodically calls consumeAudio().
   // Called on the WebAudio audio thread.
   void consumeAudio(const blink::WebVector<const float*>& audio_data,
                     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:
   // Called by AudioPushFifo zero or more times during the call to
   // consumeAudio().  Delivers audio data with the required buffer size to the
   // track.
   void DeliverRebufferedAudio(const media::AudioBus& audio_bus,
                               int frame_delay);
 
-  // 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_;
 
   media::AudioParameters params_;
 
   // Flag to help notify the |track_| when the audio format has changed.
   bool audio_format_changed_;
 
   // A wrapper used for providing audio to |fifo_|.
   scoped_ptr<media::AudioBus> wrapper_bus_;
 
@@ skipping 14 matching lines @@
   // This object registers with a blink::WebMediaStreamSource. We keep track of
   // that in order to be able to deregister before stopping the audio track.
   blink::WebMediaStreamSource blink_source_;
 
   DISALLOW_COPY_AND_ASSIGN(WebAudioCapturerSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_WEBAUDIO_CAPTURER_SOURCE_H_