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..b37f7cb0ad5bf96271e7648a3a8d544f0aa28027 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"
 #include "base/time/tick_clock.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/auto_open_close_event.h"
 #include "cc/layers/video_frame_provider.h"
 #include "media/base/video_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
@@ -160,6 +162,14 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor
   base::Lock callback_lock_;
   VideoRendererSink::RenderCallback* callback_;
 
+  // AutoOpenCloseEvent for begin/end events. We need to also store the
+  // task runner on which this class is constructed (this is not necessarily
+  // the same as compositor_task_runner_) because the AutoOpenCloseEvent
+  // functions must be calle don the same thread where the AutoOpenCloseEvent
+  // itself is constructed.
+  base::trace_event::AutoOpenCloseEvent* auto_open_close_;

[benjhayden, 2016/10/12 20:41:10]

std::unique_ptr<AOCE> aoce_;

[alexandermont, 2016/10/13 19:15:53]

Done

+  scoped_refptr<base::SingleThreadTaskRunner> constructor_task_runner_;
+
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };