Implement disabling and enabling media tracks

media/mojo/services/mojo_demuxer_stream_adapter.h

Index: media/mojo/services/mojo_demuxer_stream_adapter.h
diff --git a/media/mojo/services/mojo_demuxer_stream_adapter.h b/media/mojo/services/mojo_demuxer_stream_adapter.h
index 5422f5590bc8fe729dbbcfed8c4215fddf20bcb3..06a39331b255ace46f1439c2333b937f9d6979af 100644
--- a/media/mojo/services/mojo_demuxer_stream_adapter.h
+++ b/media/mojo/services/mojo_demuxer_stream_adapter.h
@@ -41,6 +41,8 @@ class MojoDemuxerStreamAdapter : public DemuxerStream {
   void EnableBitstreamConverter() override;
   bool SupportsConfigChanges() override;
   VideoRotation video_rotation() override;
+  bool enabled() const override;
+  void set_enabled(bool enabled, base::TimeDelta timestamp) override;
 
  private:
   void OnStreamReady(mojom::DemuxerStream::Type type,
@@ -75,6 +77,8 @@ class MojoDemuxerStreamAdapter : public DemuxerStream {
 
   DemuxerStream::Type type_;
 
+  bool enabled_ = true;
+
   // DataPipe for deserializing the data section of DecoderBuffers from.
   mojo::ScopedDataPipeConsumerHandle stream_pipe_;