Use enum instead of string in MessageLoopFactory::GetMessageLoop*

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 "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/decryptor.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/video_decoder.h"
 
-class MessageLoop;
-
 struct AVCodecContext;
 struct AVFrame;
 
+namespace base {
+class MessageLoopProxy;
+}
+
 namespace media {
 
 class DecoderBuffer;
 
 class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
  public:
-  FFmpegVideoDecoder(const base::Callback<MessageLoop*()>& message_loop_cb,
+  typedef base::Callback<
+      scoped_refptr<base::MessageLoopProxy>()> MessageLoopFactoryCB;
+  FFmpegVideoDecoder(const MessageLoopFactoryCB& message_loop_factory_cb,
                      Decryptor* decryptor);
 
   // VideoDecoder implementation.
   virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
                           const PipelineStatusCB& status_cb,
                           const StatisticsCB& statistics_cb) OVERRIDE;
   virtual void Read(const ReadCB& read_cb) OVERRIDE;
   virtual void Reset(const base::Closure& closure) OVERRIDE;
   virtual void Stop(const base::Closure& closure) OVERRIDE;
 
@@ skipping 44 matching lines @@
   // and resets them to NULL.
   void ReleaseFFmpegResources();
 
   // Reset decoder and call |reset_cb_|.
   void DoReset();
 
   // Free decoder resources and call |stop_cb_|.
   void DoStop();
 
   // This is !is_null() iff Initialize() hasn't been called.
-  base::Callback<MessageLoop*()> message_loop_factory_cb_;
+  MessageLoopFactoryCB message_loop_factory_cb_;
 
-  MessageLoop* message_loop_;
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
 
   DecoderState state_;
 
   StatisticsCB statistics_cb_;
 
   ReadCB read_cb_;
   base::Closure reset_cb_;
   base::Closure stop_cb_;
 
   // FFmpeg structures owned by this object.
   AVCodecContext* codec_context_;
   AVFrame* av_frame_;
 
   // Pointer to the demuxer stream that will feed us compressed buffers.
   scoped_refptr<DemuxerStream> demuxer_stream_;
 
   Decryptor* decryptor_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegVideoDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_VIDEO_DECODER_H_