Make TracedValue lower overhead.

base/debug/trace_event_object.h

+// Copyright 2013 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 BASE_DEBUG_TRACED_OBJECT_H_
+#define BASE_DEBUG_TRACED_OBJECT_H_
+
+#include "base/debug/trace_event_value.h"
+
+namespace base {
+namespace debug {
+
+class TracedValue;
+
+class BASE_EXPORT TracedObject {
+ public:
+  virtual ~TracedObject() {}
+  virtual void PushInto(base::debug::TracedValue* traced_value) const = 0;
+};
+
+}  // namespace debug
+}  // namespace base
+
+#endif
+