Basic media tracks implementation for media stream parsers

media/formats/mpeg/mpeg_audio_stream_parser_base.cc

Index: media/formats/mpeg/mpeg_audio_stream_parser_base.cc
diff --git a/media/formats/mpeg/mpeg_audio_stream_parser_base.cc b/media/formats/mpeg/mpeg_audio_stream_parser_base.cc
index ea2261fad7965e572c61b9acfcf94ac28745431c..202849527de0b103fbde90942ce626de3f68d404 100644
--- a/media/formats/mpeg/mpeg_audio_stream_parser_base.cc
+++ b/media/formats/mpeg/mpeg_audio_stream_parser_base.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/message_loop/message_loop.h"
+#include "media/base/media_tracks.h"
 #include "media/base/stream_parser_buffer.h"
 #include "media/base/text_track_config.h"
 #include "media/base/timestamp_constants.h"
@@ -220,8 +221,11 @@ int MPEGAudioStreamParserBase::ParseFrame(const uint8_t* data,
     timestamp_helper_.reset(new AudioTimestampHelper(sample_rate));
     timestamp_helper_->SetBaseTimestamp(base_timestamp);
 
-    VideoDecoderConfig video_config;
-    if (!config_cb_.Run(config_, video_config, TextTrackConfigMap()))
+    scoped_ptr<MediaTracks> media_tracks(new MediaTracks());
+    if (config_.IsValidConfig()) {

[wolenetz, 2016/02/26 00:06:21]

Hmm. Do we instead want to preserve the potential for invalid codec config to be
in |tracks| for use in determining in InitSegmentReceivedCB a particular error
path or error message?

[servolk, 2016/02/26 01:56:33]

I think it's better to just pass an empty MediaTracks collection to higher
levels, the MSE spec explicitly prescribes how to handle that (see step #2 in
https://w3c.github.io/media-source/#sourcebuffer-init-segment-received).

[wolenetz, 2016/02/26 19:29:27]

Ack. If we need more info on why a particular expected-to-be-valid codec config
wasn't present in a MediaTracks, we'd probably need to log this reason somewhere
in the parser, not at that higher level, so sgtm.

+      media_tracks->AddAudioTrack(config_, "audio", "", "", "");
+    }
+    if (!config_cb_.Run(std::move(media_tracks), TextTrackConfigMap()))
       return -1;
 
     if (!init_cb_.is_null()) {