Add tracing AutoOpenCloseEvent.

base/trace_event/vfc_persistent_async_event.cc

+// Copyright 2016 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 "base/macros.h"
+#include "base/trace_event/trace_event.h"
+#include "base/trace_event/vfc_persistent_async_event.h"
+
+namespace base {
+namespace trace_event {
+
+VFCPersistentAsyncEvent::VFCPersistentAsyncEvent() {}
+
+VFCPersistentAsyncEvent::~VFCPersistentAsyncEvent() {}
+
+void VFCPersistentAsyncEvent::RecordStartEvent() {      
+        TRACE_EVENT1("media", "VideoFrameCompositor::Start", "video_id", param_value_);
+}
+
+void VFCPersistentAsyncEvent::RecordStopEvent() {
+        TRACE_EVENT1("media", "VideoFrameCompositor::Stop", "video_id", param_value_);
+}
+
+void VFCPersistentAsyncEvent::RecordStartEventWithOffset(double offset) {

[charliea (OOO until 10-5), 2016/07/19 20:27:18]

Unless we need something like this immediately, I'd say not to add it for now.
We should keep in mind that it might be necessary in the future though and make
it so that the API can be easily altered to allow this option.

+        TRACE_EVENT2("media", "VideoFrameCompositor::Start", "video_id", param_value_, "offset", offset);
+}
+
+}
+}