The DOMRectReadOnly interface requires serializer.

third_party/WebKit/Source/core/dom/DOMRectReadOnly.cpp

 // 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 "core/dom/DOMRectReadOnly.h"
 
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/V8ObjectBuilder.h"
+
 namespace blink {
 
 DOMRectReadOnly* DOMRectReadOnly::create(double x,
                                          double y,
                                          double width,
                                          double height) {
   return new DOMRectReadOnly(x, y, width, height);
 }
 
+ScriptValue DOMRectReadOnly::toJSONForBinding(ScriptState* scriptState) const {
+  V8ObjectBuilder result(scriptState);
+  result.addNumber("x", x());
+  result.addNumber("y", y());
+  result.addNumber("width", width());
+  result.addNumber("height", height());
+  result.addNumber("top", top());
+  result.addNumber("right", right());
+  result.addNumber("bottom", bottom());
+  result.addNumber("left", left());
+  return result.scriptValue();
+}
+
 DOMRectReadOnly::DOMRectReadOnly(double x,
                                  double y,
                                  double width,
                                  double height)
     : m_x(x), m_y(y), m_width(width), m_height(height) {}
 
 }  // namespace blink