Add tracing AutoOpenCloseEvent.

media/blink/video_frame_compositor.h

Index: media/blink/video_frame_compositor.h
diff --git a/media/blink/video_frame_compositor.h b/media/blink/video_frame_compositor.h
index 9bb79fd056a9651221652435bc2ca29103973661..b21fc0d78145f6d318503b3dfedb9519b45ac55c 100644
--- a/media/blink/video_frame_compositor.h
+++ b/media/blink/video_frame_compositor.h
@@ -14,6 +14,7 @@
 #include "base/synchronization/lock.h"
 #include "base/time/tick_clock.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/vfc_persistent_async_event.h"
 #include "cc/layers/video_frame_provider.h"
 #include "media/base/video_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
@@ -135,6 +136,9 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor
   scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
   std::unique_ptr<base::TickClock> tick_clock_;
 
+  // Persistent async event
+  base::trace_event::VFCPersistentAsyncEvent* persistent_async_ = nullptr;
+
   // Allows tests to disable the background rendering task.
   bool background_rendering_enabled_;