Use chromium trace_event implementation in blink

third_party/WebKit/Source/platform/TracedValue.h

 // 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.
 
 #ifndef TracedValue_h
 #define TracedValue_h
 
-#include "base/memory/ref_counted.h"
-#include "platform/EventTracer.h"
+#include "base/trace_event/trace_event_argument.h"
+#include "platform/PlatformExport.h"
 #include "wtf/text/WTFString.h"
-#include <memory>
-
-namespace base {
-namespace trace_event {
-class TracedValue;
-}
-}
 
 namespace blink {
 
 // TracedValue copies all passed names and values and doesn't retain references.
-class PLATFORM_EXPORT TracedValue final {
+class PLATFORM_EXPORT TracedValue final : public base::trace_event::ConvertableToTraceFormat {
     WTF_MAKE_NONCOPYABLE(TracedValue);
 
 public:
     ~TracedValue();
 
     static std::unique_ptr<TracedValue> create();
 
     void endDictionary();
     void endArray();
 
     void setInteger(const char* name, int value);
     void setDouble(const char* name, double);
     void setBoolean(const char* name, bool value);
     void setString(const char* name, const String& value);
     void beginArray(const char* name);
     void beginDictionary(const char* name);
 
     void pushInteger(int);
     void pushDouble(double);
     void pushBoolean(bool);
     void pushString(const String&);
     void beginArray();
     void beginDictionary();
 
     String toString() const;
 
 private:
     TracedValue();
 
-    // This will be moved (and become null) when TracedValue is passed to
-    // EventTracer::addTraceEvent().
-    std::unique_ptr<base::trace_event::TracedValue> m_tracedValue;
+    // ConvertableToTraceFormat
+    using base::trace_event::ConvertableToTraceFormat::ToString; // Hide this method from blink code.
+    void AppendAsTraceFormat(std::string*) const final;
+    void EstimateTraceMemoryOverhead(base::trace_event::TraceEventMemoryOverhead*) final;
 
-    friend class EventTracer;
+    base::trace_event::TracedValue m_tracedValue;
 };
 
 } // namespace blink
 
 #endif // TracedValue_h