Assign correct track ids to buffers emitted from StreamParsers

media/formats/mp2t/mp2t_common.h

Index: media/formats/mp2t/mp2t_common.h
diff --git a/media/formats/mp2t/mp2t_common.h b/media/formats/mp2t/mp2t_common.h
index 5c8947569c9a51eed1973749f02cb3a9b275e161..37e5891bb154ebdde76addb2db75ea3048958c80 100644
--- a/media/formats/mp2t/mp2t_common.h
+++ b/media/formats/mp2t/mp2t_common.h
@@ -17,4 +17,11 @@
       } \
     } while (0)
 
+namespace media {
+namespace mp2t {
+const int kMp2tAudioTrackId = 1;
+const int kMp2tVideoTrackId = 2;
+}  // namespace media
+}  // namespace mp2t
+
 #endif  // MEDIA_FORMATS_MP2T_MP2T_COMMON_H_