Remove reference counting from media::DemuxerStream and friends.

media/base/demuxer_stream.h

Index: media/base/demuxer_stream.h
diff --git a/media/base/demuxer_stream.h b/media/base/demuxer_stream.h
index 30ef1ec7e6cbda97fe2417b6de538501b21f5ec3..284bcf0f2a794c3a18bfc4e5fcb08552c223584e 100644
--- a/media/base/demuxer_stream.h
+++ b/media/base/demuxer_stream.h
@@ -16,8 +16,7 @@ class AudioDecoderConfig;
 class DecoderBuffer;
 class VideoDecoderConfig;
 
-class MEDIA_EXPORT DemuxerStream
-    : public base::RefCountedThreadSafe<DemuxerStream> {
+class MEDIA_EXPORT DemuxerStream {
  public:
   enum Type {
     UNKNOWN,
@@ -70,7 +69,7 @@ class MEDIA_EXPORT DemuxerStream
   virtual void EnableBitstreamConverter() = 0;
 
  protected:
-  friend class base::RefCountedThreadSafe<DemuxerStream>;
+  // Only allow concrete implementations to get deleted.
   virtual ~DemuxerStream();
 };