MSE: Record counts of detected MSE audio, video and text tracks

media/formats/mp4/box_definitions.h

Index: media/formats/mp4/box_definitions.h
diff --git a/media/formats/mp4/box_definitions.h b/media/formats/mp4/box_definitions.h
index 24b585bac0f910923db4e1e5f36d80682828ea8b..b2566764aa9484289dbd86d8ab0aa1cd9747d719 100644
--- a/media/formats/mp4/box_definitions.h
+++ b/media/formats/mp4/box_definitions.h
@@ -24,12 +24,7 @@
 namespace media {
 namespace mp4 {
 
-enum TrackType {
-  kInvalid = 0,
-  kVideo,
-  kAudio,
-  kHint
-};
+enum TrackType { kInvalid = 0, kVideo, kAudio, kText, kHint };
 
 enum SampleFlags {
   kSampleIsNonSyncSample = 0x10000