Unify media track info reporting on a demuxer level

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index ffd9c220ed495d9cd90b111da4d2664d04e35e77..c5c33678345b24e85da4f317cf9270a4d794a354 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -18,6 +18,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread.h"
 #include "build/build_config.h"
+#include "media/base/media_tracks.h"
 #include "media/base/pipeline_impl.h"
 #include "media/base/renderer_factory.h"
 #include "media/base/surface_manager.h"
@@ -261,6 +262,11 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   void OnEncryptedMediaInitData(EmeInitDataType init_data_type,
                                 const std::vector<uint8_t>& init_data);
 
+  // Called when the FFmpegDemuxer encounters new media tracks. This is only
+  // invoked when using FFmpegDemuxer, since MSE/ChunkDemuxer handle media
+  // tracks separately in WebSourceBufferImpl.
+  void OnFFmpegMediaTracksUpdated(scoped_ptr<MediaTracks> tracks);

[wolenetz, 2016/03/05 01:47:43]

Hmm. Having distinct routes for reporting this info into blink src= vs MSE
smells funny on first look, but I'm not sure immediately of a better way.

[servolk, 2016/03/05 01:56:19]

I've spend quite a bit of time trying different approaches, and at this point
I'm pretty sure that this is the right way to do this. See further CLs to see
how it all ties together. I've already been able to verify this approach with
basic layout tests on blink level for both FFmpeg and MSE!

+
   // Called when a decoder detects that the key needed to decrypt the stream
   // is not available.
   void OnWaitingForDecryptionKey();