Replace scoped_ptr with std::unique_ptr in //media/base.

media/base/media_tracks.h

Index: media/base/media_tracks.h
diff --git a/media/base/media_tracks.h b/media/base/media_tracks.h
index 4e0fbb0fc1f88195ce14cc05d14a424924be4d5d..ea4a38c18d8bbb3dc05dcee23c5ee82966eb97f0 100644
--- a/media/base/media_tracks.h
+++ b/media/base/media_tracks.h
@@ -6,11 +6,11 @@
 #define MEDIA_BASE_MEDIA_TRACKS_H_
 
 #include <map>
+#include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 #include "media/base/media_track.h"
 
@@ -21,7 +21,7 @@ class VideoDecoderConfig;
 
 class MEDIA_EXPORT MediaTracks {
  public:
-  typedef std::vector<scoped_ptr<MediaTrack>> MediaTracksCollection;
+  using MediaTracksCollection = std::vector<std::unique_ptr<MediaTrack>>;
 
   MediaTracks();
   ~MediaTracks();