Implement reading of media track info from WebM and MP4 containers

media/formats/webm/webm_stream_parser.h

Index: media/formats/webm/webm_stream_parser.h
diff --git a/media/formats/webm/webm_stream_parser.h b/media/formats/webm/webm_stream_parser.h
index 6de1deda98f6892fe3a29ab43a609035e4b8cbc6..78f14976e79a88ac3e75a571906afbfdaa16b361 100644
--- a/media/formats/webm/webm_stream_parser.h
+++ b/media/formats/webm/webm_stream_parser.h
@@ -12,6 +12,7 @@
 #include "base/memory/ref_counted.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/byte_queue.h"
+#include "media/base/media_export.h"
 #include "media/base/stream_parser.h"
 #include "media/base/video_decoder_config.h"
 
@@ -19,7 +20,7 @@ namespace media {
 
 class WebMClusterParser;
 
-class WebMStreamParser : public StreamParser {
+class MEDIA_EXPORT WebMStreamParser : public StreamParser {
  public:
   WebMStreamParser();
   ~WebMStreamParser() override;