Oilpan: fix build after r197830.

Source/core/inspector/LayoutEditor.cpp

 // Copyright 2015 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 "config.h"
 #include "core/inspector/LayoutEditor.h"
 
 #include "core/css/CSSComputedStyleDeclaration.h"
 #include "core/css/CSSPrimitiveValue.h"
 #include "core/frame/FrameView.h"
@@ skipping 41 matching lines @@
 } // namespace
 
 LayoutEditor::LayoutEditor(InspectorCSSAgent* cssAgent)
     : m_node(nullptr)
     , m_cssAgent(cssAgent)
     , m_changingProperty(CSSPropertyInvalid)
     , m_propertyInitialValue(0)
 {
 }
 
+DEFINE_TRACE(LayoutEditor)
+{
+    visitor->trace(m_node);
+    visitor->trace(m_cssAgent);
+}
+
 void LayoutEditor::setNode(Node* node)
 {
     m_node = node;
     m_changingProperty = CSSPropertyInvalid;
     m_propertyInitialValue = 0;
 }
 
 PassRefPtr<JSONObject> LayoutEditor::buildJSONInfo() const
 {
     if (!m_node)
@@ skipping 71 matching lines @@
         m_cssAgent->setCSSPropertyValue(m_node.get(), m_changingProperty, cssDelta + m_propertyInitialValue);
 }
 
 void LayoutEditor::overlayEndedPropertyChange()
 {
     m_changingProperty = CSSPropertyInvalid;
     m_propertyInitialValue = 0;
 }
 
 } // namespace blink