Add support for config changes during playback to FFmpegVideoDecoder.

media/filters/ffmpeg_video_decoder.h

Index: media/filters/ffmpeg_video_decoder.h
diff --git a/media/filters/ffmpeg_video_decoder.h b/media/filters/ffmpeg_video_decoder.h
index a48e3b4b841024db0d326e907c7c313ad4aec8fb..340864db5a8259d907a73ef8980b0d009b45ed98 100644
--- a/media/filters/ffmpeg_video_decoder.h
+++ b/media/filters/ffmpeg_video_decoder.h
@@ -80,6 +80,10 @@ class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
   bool Decode(const scoped_refptr<DecoderBuffer>& buffer,
               scoped_refptr<VideoFrame>* video_frame);
 
+  // Handles (re-)initializing the decoder with a (new) config.
+  // Returns true if initialization was successful.
+  bool ConfigureDecoder();
+
   // Releases resources associated with |codec_context_| and |av_frame_|
   // and resets them to NULL.
   void ReleaseFFmpegResources();