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..1229df0398c2c0d148d350ae4c26b98025be2891 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"
 
@@ -35,7 +36,8 @@ VideoFrameCompositor::VideoFrameCompositor(
       new_background_frame_(false),
       // Assume 60Hz before the first UpdateCurrentFrame() call.
       last_interval_(base::TimeDelta::FromSecondsD(1.0 / 60)),
-      callback_(nullptr) {
+      callback_(nullptr),
+      auto_open_close_(nullptr) {
   background_rendering_timer_.SetTaskRunner(compositor_task_runner_);
 }
 
@@ -43,6 +45,8 @@ VideoFrameCompositor::~VideoFrameCompositor() {
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());

[benjhayden, 2016/10/11 21:42:19]

You're deleting auto_open_close_ on the compositor_task_runner_ thread. That
looks right to me.

   DCHECK(!callback_);
   DCHECK(!rendering_);
+  if (auto_open_close_)
+    delete auto_open_close_;
   if (client_)
     client_->StopUsingProvider();
 }
@@ -105,8 +109,12 @@ bool VideoFrameCompositor::HasCurrentFrame() {
 }
 
 void VideoFrameCompositor::Start(RenderCallback* callback) {
-  TRACE_EVENT_ASYNC_BEGIN0("media,rail", "VideoPlayback",
-                           static_cast<const void*>(this));
+  if (auto_open_close_ == nullptr) {

[benjhayden, 2016/10/11 21:42:19]

It looks like you're creating this and calling Begin and End on the media
thread, so move this code to OnRendererStateUpdate so that it runs on the
compositor_task_runner_ thread.

+    auto_open_close_ = new base::trace_event::AutoOpenCloseEvent(
+        base::trace_event::AutoOpenCloseEvent::Type::ASYNC, "media,rail",
+        "VideoPlayback");
+  }
+  auto_open_close_->Begin();
 
   // 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.
@@ -119,8 +127,7 @@ void VideoFrameCompositor::Start(RenderCallback* callback) {
 }
 
 void VideoFrameCompositor::Stop() {
-  TRACE_EVENT_ASYNC_END0("media,rail", "VideoPlayback",
-                         static_cast<const void*>(this));
+  auto_open_close_->End();
 
   // Called from the media thread, so release the callback under lock before
   // returning to avoid a pending UpdateCurrentFrame() call occurring before