Oilpan: Prepare to move RenderObject and RenderObjectChildList to Oilpan heap.

Source/core/rendering/RenderFullScreen.cpp

 /*
  * Copyright (C) 2010 Apple 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
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 34 matching lines @@
 };
 
 void RenderFullScreenPlaceholder::willBeDestroyed()
 {
     m_owner->setPlaceholder(0);
     RenderBlock::willBeDestroyed();
 }
 
 RenderFullScreen::RenderFullScreen()
     : RenderFlexibleBox(0)
-    , m_placeholder(0)
+    , m_placeholder(nullptr)
 {
     setReplaced(false);
 }
 
 RenderFullScreen* RenderFullScreen::createAnonymous(Document* document)
 {
     RenderFullScreen* renderer = new RenderFullScreen();
     renderer->setDocumentForAnonymous(document);
     return renderer;
 }
 
+void RenderFullScreen::trace(Visitor* visitor)
+{
+    visitor->trace(m_placeholder);
+    RenderFlexibleBox::trace(visitor);
+}
+
 void RenderFullScreen::willBeDestroyed()
 {
     if (m_placeholder) {
         remove();
         if (!m_placeholder->beingDestroyed())
             m_placeholder->destroy();
         ASSERT(!m_placeholder);
     }
 
     // RenderObjects are unretained, so notify the document (which holds a pointer to a RenderFullScreen)
@@ skipping 110 matching lines @@
     if (!m_placeholder) {
         m_placeholder = new RenderFullScreenPlaceholder(this);
         m_placeholder->setStyle(style);
         if (parent()) {
             parent()->addChild(m_placeholder, this);
             parent()->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation();
         }
     } else
         m_placeholder->setStyle(style);
 }