Implement disabling and enabling media tracks

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 596ab67e83692aba287f11e6c1488a623ffee8e6..17f193f24acb06c420bd3f00f674da55778dd24f 100644
--- a/media/base/demuxer_stream.h
+++ b/media/base/demuxer_stream.h
@@ -7,6 +7,7 @@
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "base/time/time.h"
 #include "media/base/media_export.h"
 #include "media/base/video_rotation.h"
 
@@ -91,6 +92,20 @@ class MEDIA_EXPORT DemuxerStream {
 
   virtual VideoRotation video_rotation() = 0;
 
+  // Indicates whether a DemuxerStream is currently enabled (i.e. should be
+  // decoded and rendered) or not.
+  virtual bool enabled() const = 0;
+
+  // Disables and re-enables the stream. Reading from a disabled stream will
+  // return an end-of-stream (EOS) buffer. When a stream is re-enabled, it needs
+  // to know the current playback position |timestamp| in order to resume
+  // reading data from a key frame preceeding the |timestamp|.
+  virtual void set_enabled(bool enabled, base::TimeDelta timestamp) = 0;
+
+  using StreamRestartedCB =
+      base::Callback<void(DemuxerStream*, base::TimeDelta)>;
+  virtual void SetStreamRestartedCB(const StreamRestartedCB& cb) = 0;
+
  protected:
   // Only allow concrete implementations to get deleted.
   virtual ~DemuxerStream();