Implement disabling and enabling media tracks

media/mojo/services/mojo_renderer_service.cc

Index: media/mojo/services/mojo_renderer_service.cc
diff --git a/media/mojo/services/mojo_renderer_service.cc b/media/mojo/services/mojo_renderer_service.cc
index 9c6f2adf0d11eb581920b6ee7244d8dadd8f09fa..52acb9a2016ddc87290eb229b7018ddff0e78cec 100644
--- a/media/mojo/services/mojo_renderer_service.cc
+++ b/media/mojo/services/mojo_renderer_service.cc
@@ -67,6 +67,21 @@ void MojoRendererService::StartPlayingFrom(int64_t time_delta_usec) {
   SchedulePeriodicMediaTimeUpdates();
 }
 
+void MojoRendererService::RestartStreamPlayback(bool video_stream,
+                                                int64_t time_delta_usec) {
+  DemuxerStream* demuxer_stream = nullptr;
+
+  if (video_stream)
+    demuxer_stream = stream_provider_->GetStream(DemuxerStream::VIDEO);
+  else
+    demuxer_stream = stream_provider_->GetStream(DemuxerStream::AUDIO);
+
+  DVLOG(2) << __FUNCTION__ << ": demuxer_stream=" << demuxer_stream
+           << " time=" << time_delta_usec;
+  renderer_->RestartStreamPlayback(
+      demuxer_stream, base::TimeDelta::FromMicroseconds(time_delta_usec));
+}
+
 void MojoRendererService::SetPlaybackRate(double playback_rate) {
   DVLOG(2) << __FUNCTION__ << ": " << playback_rate;
   DCHECK_EQ(state_, STATE_PLAYING);