Adding ChunkDemuxer implementation.

media/filters/ffmpeg_demuxer.cc

Index: media/filters/ffmpeg_demuxer.cc
diff --git a/media/filters/ffmpeg_demuxer.cc b/media/filters/ffmpeg_demuxer.cc
index dd2d96b3583e1193cc0a63902cef2248c7a97b44..c5c073251788eb69b2fe16945867936525968eca 100644
--- a/media/filters/ffmpeg_demuxer.cc
+++ b/media/filters/ffmpeg_demuxer.cc
@@ -276,28 +276,7 @@ FFmpegDemuxer::~FFmpegDemuxer() {
   // in the decoder filters. By reaching this point, all filters should have
   // stopped, so this is the only safe place to do the global clean up.
   // TODO(hclam): close the codecs in the corresponding decoders.
-  if (!format_context_)
-    return;
-
-  // Iterate each stream and destroy each one of them.
-  int streams = format_context_->nb_streams;
-  for (int i = 0; i < streams; ++i) {
-    AVStream* stream = format_context_->streams[i];
-
-    // The conditions for calling avcodec_close():
-    // 1. AVStream is alive.
-    // 2. AVCodecContext in AVStream is alive.
-    // 3. AVCodec in AVCodecContext is alive.
-    // Notice that closing a codec context without prior avcodec_open() will
-    // result in a crash in FFmpeg.
-    if (stream && stream->codec && stream->codec->codec) {
-      stream->discard = AVDISCARD_ALL;
-      avcodec_close(stream->codec);
-    }
-  }
-
-  // Then finally cleanup the format context.
-  av_close_input_file(format_context_);
+  DestroyAVFormatContext(format_context_);
   format_context_ = NULL;
 }