Oilpan: Prepare moving InspectorOverlayHost to Oilpan

Source/core/inspector/InspectorOverlayHost.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 15 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 
 #include "core/inspector/InspectorOverlayHost.h"
 
 namespace blink {
 
 InspectorOverlayHost::InspectorOverlayHost()
-    : m_listener(0)
+    : m_listener(nullptr)
 {
     ScriptWrappable::init(this);
 }
 
 InspectorOverlayHost::~InspectorOverlayHost()
 {
 }
 
 void InspectorOverlayHost::resume()
 {
     if (m_listener)
         m_listener->overlayResumed();
 }
 
 void InspectorOverlayHost::stepOver()
 {
     if (m_listener)
         m_listener->overlaySteppedOver();
 }
 
+void InspectorOverlayHost::trace(Visitor* visitor)
+{
+    visitor->trace(m_listener);
+}
+
 } // namespace blink