WebmMuxer-MediaRecorderHandler: thread hopping and data ownership

content/renderer/media/media_recorder_handler.cc

 // Copyright 2015 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.
 
 #include "content/renderer/media/media_recorder_handler.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "content/renderer/media/video_track_recorder.h"
 #include "media/base/bind_to_current_loop.h"
 #include "media/capture/webm_muxer.h"
 #include "third_party/WebKit/public/platform/WebMediaRecorderHandlerClient.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 
 namespace content {
 
 MediaRecorderHandler::MediaRecorderHandler()
     : recording_(false), client_(nullptr), weak_factory_(this) {
   DVLOG(3) << __FUNCTION__;
+  webm_muxer_ = make_scoped_refptr(
+      new media::WebmMuxer(base::MessageLoop::current()->task_runner(),
+                           media::BindToCurrentLoop(
+                               base::Bind(&MediaRecorderHandler::WriteData,
+                               weak_factory_.GetWeakPtr()))));
 }
 
 MediaRecorderHandler::~MediaRecorderHandler() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   // Send a |last_in_slice| to our |client_|.
   if (client_)
     client_->writeData(nullptr, 0u, true);
 }
 
 bool MediaRecorderHandler::canSupportMimeType(
@@ skipping 22 matching lines @@
 bool MediaRecorderHandler::start() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(!recording_);
   return start(0);
 }
 
 bool MediaRecorderHandler::start(int timeslice) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(!recording_);
   DCHECK(!media_stream_.isNull());
-
-  webm_muxer_.reset(new media::WebmMuxer(media::BindToCurrentLoop(base::Bind(
-      &MediaRecorderHandler::WriteData, weak_factory_.GetWeakPtr()))));
   DCHECK(webm_muxer_);
 
   blink::WebVector<blink::WebMediaStreamTrack> video_tracks;
   media_stream_.videoTracks(video_tracks);
 
   if (video_tracks.isEmpty()) {
     // TODO(mcasas): Add audio_tracks and update the code in this function
     // correspondingly, see http://crbug.com/528519. As of now, only video
     // tracks are supported.
     LOG(WARNING) << "Recording no video tracks is not implemented";
     return false;
   }
   // TODO(mcasas): The muxer API supports only one video track. Extend it to
   // several video tracks, see http://crbug.com/528523.
   LOG_IF(WARNING, video_tracks.size() > 1u) << "Recording multiple video"
       << " tracks is not implemented.  Only recording first video track.";
   const blink::WebMediaStreamTrack& video_track = video_tracks[0];
   if (video_track.isNull())
     return false;
 
   const VideoTrackRecorder::OnEncodedVideoCB on_encoded_video_cb =
-      base::Bind(&media::WebmMuxer::OnEncodedVideo,
-                 base::Unretained(webm_muxer_.get()));
+      base::Bind(&media::WebmMuxer::OnEncodedVideo, webm_muxer_);
 
   video_recorders_.push_back(new VideoTrackRecorder(video_track,
                                                     on_encoded_video_cb));
 
   recording_ = true;
   return true;
 }
 
 void MediaRecorderHandler::stop() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(recording_);
 
   recording_ = false;
   video_recorders_.clear();
-  webm_muxer_.reset(NULL);
 }
 
 void MediaRecorderHandler::pause() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(recording_);
   recording_ = false;
   NOTIMPLEMENTED();
 }
 
 void MediaRecorderHandler::resume() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   DCHECK(!recording_);
   recording_ = true;
   NOTIMPLEMENTED();
 }
 
 void MediaRecorderHandler::WriteData(const base::StringPiece& data) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   client_->writeData(data.data(), data.size(), false  /* lastInSlice */);
 }
 
 void MediaRecorderHandler::OnVideoFrameForTesting(
     const scoped_refptr<media::VideoFrame>& frame,
     const base::TimeTicks& timestamp) {
   for (auto* recorder : video_recorders_)
     recorder->OnVideoFrameForTesting(frame, timestamp);
 }
 
 }  // namespace content