Revert of media::FFmpegVideoDecoder: remove ctor param |task_runner| and use a ThreadChecker instead.

media/filters/ffmpeg_video_decoder.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 MEDIA_FILTERS_FFMPEG_VIDEO_DECODER_H_
 #define MEDIA_FILTERS_FFMPEG_VIDEO_DECODER_H_
 
 #include <list>
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/threading/thread_checker.h"
 #include "media/base/video_decoder.h"
 #include "media/base/video_decoder_config.h"
 #include "media/base/video_frame_pool.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 
 struct AVCodecContext;
 struct AVFrame;
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
 
 class DecoderBuffer;
 
 class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
  public:
   static bool IsCodecSupported(VideoCodec codec);
 
-  FFmpegVideoDecoder();
+  explicit FFmpegVideoDecoder(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
   ~FFmpegVideoDecoder() override;
 
   // Allow decoding of individual NALU. Entire frames are required by default.
   // Disables low-latency mode. Must be called before Initialize().
   void set_decode_nalus(bool decode_nalus) { decode_nalus_ = decode_nalus; }
 
   // VideoDecoder implementation.
   std::string GetDisplayName() const override;
   void Initialize(const VideoDecoderConfig& config,
                   bool low_delay,
@@ skipping 24 matching lines @@
                     bool* has_produced_frame);
 
   // Handles (re-)initializing the decoder with a (new) config.
   // Returns true if initialization was successful.
   bool ConfigureDecoder(bool low_delay);
 
   // Releases resources associated with |codec_context_| and |av_frame_|
   // and resets them to NULL.
   void ReleaseFFmpegResources();
 
-  base::ThreadChecker thread_checker_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   DecoderState state_;
 
   OutputCB output_cb_;
 
   // FFmpeg structures owned by this object.
   scoped_ptr<AVCodecContext, ScopedPtrAVFreeContext> codec_context_;
   scoped_ptr<AVFrame, ScopedPtrAVFreeFrame> av_frame_;
 
   VideoDecoderConfig config_;
 
   VideoFramePool frame_pool_;
 
   bool decode_nalus_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegVideoDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_VIDEO_DECODER_H_