Add tracing AutoOpenCloseEvent.

media/blink/video_frame_compositor.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
 #define MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
 
 #include <utility>
+#include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "base/time/tick_clock.h"
 #include "base/timer/timer.h"
 #include "cc/layers/video_frame_provider.h"
 #include "media/base/video_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
 #include "ui/gfx/geometry/size.h"
+#include "base/trace_event/vfc_persistent_async_event.h"
 
 namespace media {
 class VideoFrame;
 
 // VideoFrameCompositor acts as a bridge between the media and cc layers for
 // rendering video frames. I.e. a media::VideoRenderer will talk to this class
 // from the media side, while a cc::VideoFrameProvider::Client will talk to it
 // from the cc side.
 //
 // This class is responsible for requesting new frames from a video renderer in
@@ skipping 95 matching lines @@
   // Updates |is_background_rendering_|, |last_interval_|, and resets
   // |background_rendering_timer_|. Returns true if there's a new frame
   // available via GetCurrentFrame().
   bool CallRender(base::TimeTicks deadline_min,
                   base::TimeTicks deadline_max,
                   bool background_rendering);
 
   scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
   std::unique_ptr<base::TickClock> tick_clock_;
 
+  // Persistent async event

[benjhayden, 2016/08/10 18:30:00]

You can remove this comment since it adds no information.

+  base::trace_event::VFCPersistentAsyncEvent* persistent_async_ = nullptr;
+  std::string video_id_;
+
   // Allows tests to disable the background rendering task.
   bool background_rendering_enabled_;
 
   // Manages UpdateCurrentFrame() callbacks if |client_| has stopped sending
   // them for various reasons.  Runs on |compositor_task_runner_| and is reset
   // after each successful UpdateCurrentFrame() call.
   base::Timer background_rendering_timer_;
 
   // These values are only set and read on the compositor thread.
   cc::VideoFrameProvider::Client* client_;
@@ skipping 11 matching lines @@
   // These values are updated and read from the media and compositor threads.
   base::Lock callback_lock_;
   VideoRendererSink::RenderCallback* callback_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_