Add tracing AutoOpenCloseEvent.

media/blink/video_frame_compositor.cc

 // 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.
 
 #include "media/blink/video_frame_compositor.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/default_tick_clock.h"
 #include "base/trace_event/trace_event.h"
+#include "base/trace_event/trace_event_impl.h"
+#include "base/trace_event/trace_log.h"
 #include "media/base/video_frame.h"
+#include "base/trace_event/vfc_persistent_async_event.h"
+
+
+#include <sstream>
+#include <string>
 
 namespace media {
 
 // Amount of time to wait between UpdateCurrentFrame() callbacks before starting
 // background rendering to keep the Render() callbacks moving.
 const int kBackgroundRenderingTimeoutMs = 250;
 
 VideoFrameCompositor::VideoFrameCompositor(
     const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner)
     : compositor_task_runner_(compositor_task_runner),
       tick_clock_(new base::DefaultTickClock()),
       background_rendering_enabled_(true),
       background_rendering_timer_(
           FROM_HERE,
           base::TimeDelta::FromMilliseconds(kBackgroundRenderingTimeoutMs),
           base::Bind(&VideoFrameCompositor::BackgroundRender,
                      base::Unretained(this)),
           // Task is not repeating, CallRender() will reset the task as needed.
           false),
       client_(nullptr),
       rendering_(false),
       rendered_last_frame_(false),
       is_background_rendering_(false),
       new_background_frame_(false),
       // Assume 60Hz before the first UpdateCurrentFrame() call.
       last_interval_(base::TimeDelta::FromSecondsD(1.0 / 60)),
       callback_(nullptr) {
   background_rendering_timer_.SetTaskRunner(compositor_task_runner_);
+  const void* this_address = static_cast<const void*>(this);
+  std::stringstream s;

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

Chrome has a handy StringPrintf library, but PersistentAsyncEvent should allow
passing a const void* to its constructor to use as the id, and allow the trace
macros to stringify it.

+  s << this_address;
+  video_id_ = s.str();
+  persistent_async_ = new base::trace_event::VFCPersistentAsyncEvent();
+  base::trace_event::TraceLog::GetInstance()->AddEnabledStateObserver(persistent_async_);
 }
 
 VideoFrameCompositor::~VideoFrameCompositor() {
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   DCHECK(!callback_);
   DCHECK(!rendering_);
   if (client_)
     client_->StopUsingProvider();
 }
 
@@ skipping 48 matching lines @@
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   return CallRender(deadline_min, deadline_max, false);
 }
 
 bool VideoFrameCompositor::HasCurrentFrame() {
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   return static_cast<bool>(current_frame_);
 }
 
 void VideoFrameCompositor::Start(RenderCallback* callback) {
-  TRACE_EVENT0("media", "VideoFrameCompositor::Start");
+  persistent_async_->Start(video_id_);
 
   // 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_);
   DCHECK(!callback_);
   callback_ = callback;
   compositor_task_runner_->PostTask(
       FROM_HERE, base::Bind(&VideoFrameCompositor::OnRendererStateUpdate,
                             base::Unretained(this), true));
 }
 
 void VideoFrameCompositor::Stop() {
-  TRACE_EVENT0("media", "VideoFrameCompositor::Stop");
+  persistent_async_->Stop(video_id_);
 
   // 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.
   base::AutoLock lock(callback_lock_);
   DCHECK(callback_);
   callback_ = nullptr;
   compositor_task_runner_->PostTask(
       FROM_HERE, base::Bind(&VideoFrameCompositor::OnRendererStateUpdate,
                             base::Unretained(this), false));
@@ skipping 103 matching lines @@
   last_interval_ = deadline_max - deadline_min;
 
   // Restart the background rendering timer whether we're background rendering
   // or not; in either case we should wait for |kBackgroundRenderingTimeoutMs|.
   if (background_rendering_enabled_)
     background_rendering_timer_.Reset();
   return new_frame || had_new_background_frame;
 }
 
 }  // namespace media