add 'slow' prefix to RenderObject's firstChild() / lastChild() methods

Source/core/rendering/RenderBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 2625 matching lines @@
     if (remainingText) {
         if (!firstLetterRemainingTextMap)
             firstLetterRemainingTextMap = new FirstLetterRemainingTextMap;
         firstLetterRemainingTextMap->set(this, remainingText);
     } else if (firstLetterRemainingTextMap)
         firstLetterRemainingTextMap->remove(this);
 }
 
 LayoutRect RenderBoxModelObject::localCaretRectForEmptyElement(LayoutUnit width, LayoutUnit textIndentOffset)
 {
-    ASSERT(!firstChild());
+    ASSERT(!slowFirstChild());
 
     // FIXME: This does not take into account either :first-line or :first-letter
     // However, as soon as some content is entered, the line boxes will be
     // constructed and this kludge is not called any more. So only the caret size
     // of an empty :first-line'd block is wrong. I think we can live with that.
     RenderStyle* currentStyle = firstLineStyle();
     LayoutUnit height = lineHeight(true, currentStyle->isHorizontalWritingMode() ? HorizontalLine : VerticalLine,  PositionOfInteriorLineBoxes);
 
     enum CaretAlignment { alignLeft, alignRight, alignCenter };
 
@@ skipping 167 matching lines @@
     ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
     for (RenderObject* child = startChild; child && child != endChild; ) {
         // Save our next sibling as moveChildTo will clear it.
         RenderObject* nextSibling = child->nextSibling();
         moveChildTo(toBoxModelObject, child, beforeChild, fullRemoveInsert);
         child = nextSibling;
     }
 }
 
 } // namespace WebCore