Ensure media's buffered ranges always have a range that includes currentTime.

media/filters/ffmpeg_demuxer.h

Index: media/filters/ffmpeg_demuxer.h
diff --git a/media/filters/ffmpeg_demuxer.h b/media/filters/ffmpeg_demuxer.h
index dee6db350313d830f67e5a02e5f0144952e67c2a..12ea44de291db8e253c8744669b20def71c91b90 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -47,11 +47,14 @@ class BitstreamConverter;
 class FFmpegDemuxer;
 class ScopedPtrAVFreePacket;
 
+typedef base::Callback<void(base::TimeDelta, base::TimeDelta)> NotifyBufferedCB;
+
 class FFmpegDemuxerStream : public DemuxerStream {
  public:
   // Keeps a copy of |demuxer| and initializes itself using information
   // inside |stream|.  Both parameters must outlive |this|.
-  FFmpegDemuxerStream(FFmpegDemuxer* demuxer, AVStream* stream);
+  FFmpegDemuxerStream(const NotifyBufferedCB& notify_buffered_cb_,

[scherkus (not reviewing), 2012/06/21 21:57:04]

is this needed given FDS has a pointer to FD and calls methods on it? (mostly an
issue w/ mixing FDS-calling-into-FD conventions)

[Ami GONE FROM CHROMIUM, 2012/06/21 22:49:02]

Yeah, I went back and forth on this.
FDS has an FD* but FD doesn't expose its host.  So to avoid this explicit
callback FD would have to increase its public API surface to either expose the
host or just expose this one method.  Given that that one method would have
exactly one caller, it seemed better to me to do it this way.
Do you feel strongly that it should go the other way?

[scherkus (not reviewing), 2012/06/21 23:18:42]

Ah! I hadn't noticed you were binding to DemuxerHost directly.

I think we're in a bit of a pickle here. 

Take a poorly muxed file w/ alternating 10 second chunks of audio and video
data. If we've demuxed the first 10 seconds of audio before getting to the first
second of video data we need to start playback -- what should we report?

1) Report [0,10] range (union of streams)
2) Report [0,1] range (intersection of streams)

Technically we should report (2) as seeking to time 9 would require fetching +
demuxing (1,9] of the video stream. ChunkDemuxer folks have implemented (2).

So -- perhaps FDS should call a method on FD and FD can crunch the intersection
+ report to host.

WDYT?

[Ami GONE FROM CHROMIUM, 2012/06/22 03:55:47]

Done % still using a CB since the stream doesn't know its own ID in the demuxer
and CB allows currying that in nicely.

+                      FFmpegDemuxer* demuxer, AVStream* stream);
 
   // Returns true is this stream has pending reads, false otherwise.
   //
@@ -107,6 +110,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   static base::TimeDelta ConvertStreamTimestamp(const AVRational& time_base,
                                                 int64 timestamp);
 
+  NotifyBufferedCB notify_buffered_cb_;
   FFmpegDemuxer* demuxer_;
   AVStream* stream_;
   AudioDecoderConfig audio_config_;
@@ -115,6 +119,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   base::TimeDelta duration_;
   bool discontinuous_;
   bool stopped_;
+  base::TimeDelta last_packet_timestamp_;
 
   typedef std::deque<scoped_refptr<DecoderBuffer> > BufferQueue;
   BufferQueue buffer_queue_;