Add tracing AutoOpenCloseEvent.

media/blink/video_frame_compositor.cc

Index: media/blink/video_frame_compositor.cc
diff --git a/media/blink/video_frame_compositor.cc b/media/blink/video_frame_compositor.cc
index 544f7098701d481c2358c2493d2f59aae52d5256..96192f501df944e83d62c6fff99ced204db5389a 100644
--- a/media/blink/video_frame_compositor.cc
+++ b/media/blink/video_frame_compositor.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/default_tick_clock.h"
+#include "base/trace_event/auto_open_close_event.h"
 #include "base/trace_event/trace_event.h"
 #include "media/base/video_frame.h"
 
@@ -52,6 +53,18 @@ void VideoFrameCompositor::OnRendererStateUpdate(bool new_state) {
   DCHECK_NE(rendering_, new_state);
   rendering_ = new_state;
 
+  if (!auto_open_close_) {
+    auto_open_close_.reset(new base::trace_event::AutoOpenCloseEvent(
+        base::trace_event::AutoOpenCloseEvent::Type::ASYNC, "media,rail",
+        "VideoPlayback"));
+  }
+
+  if (rendering_) {
+    auto_open_close_->Begin();
+  } else {
+    auto_open_close_->End();
+  }
+
   if (rendering_) {
     // Always start playback in background rendering mode, if |client_| kicks
     // in right away it's okay.
@@ -105,9 +118,6 @@ bool VideoFrameCompositor::HasCurrentFrame() {
 }
 
 void VideoFrameCompositor::Start(RenderCallback* callback) {
-  TRACE_EVENT_ASYNC_BEGIN0("media,rail", "VideoPlayback",
-                           static_cast<const void*>(this));
-
   // Called from the media thread, so acquire the callback under lock before
   // returning in case a Stop() call comes in before the PostTask is processed.
   base::AutoLock lock(callback_lock_);
@@ -119,9 +129,6 @@ void VideoFrameCompositor::Start(RenderCallback* callback) {
 }
 
 void VideoFrameCompositor::Stop() {
-  TRACE_EVENT_ASYNC_END0("media,rail", "VideoPlayback",
-                         static_cast<const void*>(this));
-
   // Called from the media thread, so release the callback under lock before
   // returning to avoid a pending UpdateCurrentFrame() call occurring before
   // the PostTask is processed.