Implement reading of media track info from WebM and MP4 containers

media/formats/webm/webm_tracks_parser.h

Index: media/formats/webm/webm_tracks_parser.h
diff --git a/media/formats/webm/webm_tracks_parser.h b/media/formats/webm/webm_tracks_parser.h
index 3569907274c6475dfb64b024f780c6c97d5e764e..6286b2303e0fa02280e246393fbf6bbc997f2c1c 100644
--- a/media/formats/webm/webm_tracks_parser.h
+++ b/media/formats/webm/webm_tracks_parser.h
@@ -18,6 +18,7 @@
 #include "base/time/time.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/media_log.h"
+#include "media/base/media_tracks.h"
 #include "media/base/text_track_config.h"
 #include "media/base/video_decoder_config.h"
 #include "media/formats/webm/webm_audio_client.h"
@@ -77,6 +78,15 @@ class MEDIA_EXPORT WebMTracksParser : public WebMParserClient {
     return text_tracks_;
   }
 
+  // Note: Calling media_tracks() method passes the ownership of the MediaTracks
+  // object from WebMTracksParser to the caller (which is typically
+  // WebMStreamParser object). So this method must be called only once, after
+  // track parsing has been completed.
+  scoped_ptr<MediaTracks> media_tracks() {
+    CHECK(media_tracks_.get());
+    return std::move(media_tracks_);
+  }
+
  private:
   // WebMParserClient implementation.
   WebMParserClient* OnListStart(int id) override;
@@ -114,6 +124,8 @@ class MEDIA_EXPORT WebMTracksParser : public WebMParserClient {
   WebMVideoClient video_client_;
   VideoDecoderConfig video_decoder_config_;
 
+  scoped_ptr<MediaTracks> media_tracks_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMTracksParser);
 };