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..a9bbab1ef19afe4e7f6a23dcff5e6a9c1304ead1 100644
--- a/media/blink/video_frame_compositor.h
+++ b/media/blink/video_frame_compositor.h
@@ -12,8 +12,10 @@
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/thread_task_runner_handle.h"

[benjhayden, 2016/10/13 21:25:41]

Is this needed?

[alexandermont, 2016/10/14 17:55:00]

Done

 #include "base/time/tick_clock.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/auto_open_close_event.h"

[Primiano Tucci (use gerrit), 2016/10/13 20:11:00]

you don't need this, you can fwd declare AOCE as long as the dtor of this class
it not implicit.
Or if you really want to keep this include here, remove from the .cc file.

[benjhayden, 2016/10/13 21:25:41]

Forward declaration is preferable because it speeds up compiling all of the
files that include this header, none of which need to know anything about AOCE
or anything that aoce.h includes.

[alexandermont, 2016/10/14 17:55:00]

Done

 #include "cc/layers/video_frame_provider.h"
 #include "media/base/video_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
@@ -160,6 +162,9 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor
   base::Lock callback_lock_;
   VideoRendererSink::RenderCallback* callback_;
 
+  // AutoOpenCloseEvent for begin/end events.
+  std::unique_ptr<base::trace_event::AutoOpenCloseEvent> auto_open_close_;
+
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };