Move Node/ContainerNode's traverseToChildAt() to NodeTraversal

Source/core/dom/RangeBoundaryPoint.h

Index: Source/core/dom/RangeBoundaryPoint.h
diff --git a/Source/core/dom/RangeBoundaryPoint.h b/Source/core/dom/RangeBoundaryPoint.h
index 7155e13e501b41746e23dcd979695c18a134f3a6..b458c7110583c997f2e8c1d343ed2da1fd8e4514 100644
--- a/Source/core/dom/RangeBoundaryPoint.h
+++ b/Source/core/dom/RangeBoundaryPoint.h
@@ -27,6 +27,7 @@
 #define RangeBoundaryPoint_h
 
 #include "core/dom/Node.h"
+#include "core/dom/NodeTraversal.h"
 #include "core/dom/Position.h"
 
 namespace blink {
@@ -124,7 +125,7 @@ inline void RangeBoundaryPoint::set(PassRefPtrWillBeRawPtr<Node> container, int
 {
     ASSERT(container);
     ASSERT(offset >= 0);
-    ASSERT(childBefore == (offset ? container->traverseToChildAt(offset - 1) : 0));
+    ASSERT(childBefore == (offset ? NodeTraversal::childAt(*container, offset - 1) : 0));
     m_containerNode = container;
     m_offsetInContainer = offset;
     m_childBeforeBoundary = childBefore;