Replace FFmpegDemuxer thread per element with base::TaskScheduler.

media/filters/ffmpeg_demuxer.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.
 
 // Implements the Demuxer interface using FFmpeg's libavformat.  At this time
 // will support demuxing any audio/video format thrown at it.  The streams
 // output mime types audio/x-ffmpeg and video/x-ffmpeg and include an integer
 // key FFmpegCodecID which contains the CodecID enumeration value.  The CodecIDs
 // can be used to create and initialize the corresponding FFmpeg decoder.
 //
@@ skipping 14 matching lines @@
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
-#include "base/threading/thread.h"
+#include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
+#include "base/single_thread_task_runner.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/decoder_buffer_queue.h"
 #include "media/base/demuxer.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/text_track_config.h"
 #include "media/base/video_decoder_config.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 #include "media/filters/blocking_url_protocol.h"
 #include "media/media_features.h"
@@ skipping 241 matching lines @@
   // Called after the streams have been collected from the media, to allow
   // the text renderer to bind each text stream to the cue rendering engine.
   void AddTextStreams();
 
   void SetLiveness(DemuxerStream::Liveness liveness);
 
   DemuxerHost* host_;
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
-  // Thread on which all blocking FFmpeg operations are executed.
-  base::Thread blocking_thread_;
+  // Blocking pool on which all blocking FFmpeg operations are executed.

[gab, 2017/02/23 21:37:10]

nit: A SequencedTaskRunner isn't a "pool", it's a "sequence". A TaskRunner would
be a "pool" but would run your tasks in parallel (depends on whether you can
accommodate for the thread-safety implications of that).

[DaleCurtis, 2017/02/23 23:07:06]

We definitely want sequence here. Updated the comment.

+  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
+
+  // Indicates if Stop() has been called.
+  bool stopped_;
 
   // Tracks if there's an outstanding av_read_frame() operation.
   //
   // TODO(scherkus): Allow more than one read in flight for higher read
   // throughput using demuxer_bench to verify improvements.
   bool pending_read_;
 
   // Tracks if there's an outstanding av_seek_frame() operation. Used to discard
   // results of pre-seek av_read_frame() operations.
   PipelineStatusCB pending_seek_cb_;
@@ skipping 61 matching lines @@
   base::WeakPtr<FFmpegDemuxer> weak_this_;
   base::WeakPtrFactory<FFmpegDemuxer> cancel_pending_seek_factory_;
   base::WeakPtrFactory<FFmpegDemuxer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_DEMUXER_H_