Move Node/ContainerNode's traverseToChildAt() to NodeTraversal

Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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 975 matching lines @@
     if (box) {
         root = box->root().nextRootBox();
         // We want to skip zero height boxes.
         // This could happen in case it is a TrailingFloatsRootInlineBox.
         if (!root || !root->logicalHeight() || !root->firstLeafChild())
             root = 0;
     }
 
     if (!root) {
         // FIXME: We need do the same in previousLinePosition.
-        Node* child = node->traverseToChildAt(p.deprecatedEditingOffset());
+        Node* child = NodeTraversal::childAt(*node, p.deprecatedEditingOffset());
         node = child ? child : &NodeTraversal::lastWithinOrSelf(*node);
         Position position = nextRootInlineBoxCandidatePosition(node, visiblePosition, editableType);
         if (position.isNotNull()) {
             RenderedPosition renderedPosition((VisiblePosition(position)));
             root = renderedPosition.rootBox();
             if (!root)
                 return VisiblePosition(position);
         }
     }
 
@@ skipping 395 matching lines @@
     int caretOffset;
     position.position().getInlineBoxAndOffset(position.affinity(), inlineBox, caretOffset);
 
     if (inlineBox)
         renderer = &inlineBox->renderer();
 
     return renderer->localCaretRect(inlineBox, caretOffset);
 }
 
 }