Generate and assign media track ids in demuxers.

media/formats/mp4/mp4_stream_parser.cc

Index: media/formats/mp4/mp4_stream_parser.cc
diff --git a/media/formats/mp4/mp4_stream_parser.cc b/media/formats/mp4/mp4_stream_parser.cc
index 1926d1fe9a5526361df6d3f201891b4307418546..3dd4ce3fd4ef7d17b3cf64448f5cc9c5ccc73fd3 100644
--- a/media/formats/mp4/mp4_stream_parser.cc
+++ b/media/formats/mp4/mp4_stream_parser.cc
@@ -318,6 +318,11 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
           codec, sample_format, channel_layout, sample_per_second, extra_data,
           is_audio_track_encrypted_ ? AesCtrEncryptionScheme() : Unencrypted(),
           base::TimeDelta(), 0);
+      if (!audio_config.IsValidConfig()) {
+        MEDIA_LOG(ERROR, media_log_) << "Invalid audio decoder config: "
+                                     << audio_config.AsHumanReadableString();
+        return false;
+      }
       has_audio_ = true;
       audio_track_id_ = track->header.track_id;
       media_tracks->AddAudioTrack(audio_config, audio_track_id_, "main",
@@ -369,6 +374,11 @@ bool MP4StreamParser::ParseMoov(BoxReader* reader) {
           // SPS/PPS are embedded in the video stream
           EmptyExtraData(),
           is_video_track_encrypted_ ? AesCtrEncryptionScheme() : Unencrypted());
+      if (!video_config.IsValidConfig()) {
+        MEDIA_LOG(ERROR, media_log_) << "Invalid video decoder config: "
+                                     << video_config.AsHumanReadableString();
+        return false;
+      }
       has_video_ = true;
       video_track_id_ = track->header.track_id;
       media_tracks->AddVideoTrack(video_config, video_track_id_, "main",