Remove DemuxerStream::GetAVStream() once and for all.

media/ffmpeg/ffmpeg_common.h

Index: media/ffmpeg/ffmpeg_common.h
diff --git a/media/ffmpeg/ffmpeg_common.h b/media/ffmpeg/ffmpeg_common.h
index 8808f45068578961e9222f847deaa3d4efa1d406..bb01f4f12e3b246a59deab1b81bf3b04e49b6513 100644
--- a/media/ffmpeg/ffmpeg_common.h
+++ b/media/ffmpeg/ffmpeg_common.h
@@ -74,8 +74,12 @@ void AudioDecoderConfigToAVCodecContext(
     const AudioDecoderConfig& config,
     AVCodecContext* codec_context);
 
-VideoCodec CodecIDToVideoCodec(CodecID codec_id);
-CodecID VideoCodecToCodecID(VideoCodec video_codec);
+void AVStreamToVideoDecoderConfig(
+    const AVStream* stream,
+    VideoDecoderConfig* config);
+void VideoDecoderConfigToAVCodecContext(
+    const VideoDecoderConfig& config,
+    AVCodecContext* codec_context);
 
 // Converts FFmpeg's channel layout to chrome's ChannelLayout.  |channels| can
 // be used when FFmpeg's channel layout is not informative in order to make a
@@ -89,12 +93,9 @@ VideoFrame::Format PixelFormatToVideoFormat(PixelFormat pixel_format);
 // Converts video formats to its corresponding FFmpeg's pixel formats.
 PixelFormat VideoFormatToPixelFormat(VideoFrame::Format video_format);
 
-// Calculates duration of one frame in the |stream| based on its frame rate.
-base::TimeDelta GetFrameDuration(AVStream* stream);
-
-// Calculates the natural width and height of the video using the video's
-// encoded dimensions and sample_aspect_ratio.
-gfx::Size GetNaturalSize(AVStream* stream);
+// Calculates the duration of one frame based on the frame rate specified by
+// |config|.
+base::TimeDelta GetFrameDuration(const VideoDecoderConfig& config);
 
 // Closes & destroys all AVStreams in the context and then closes &
 // destroys the AVFormatContext.