Use new Traversal<HTML*Element> API in HTML code

Source/core/html/HTMLTableSectionElement.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2010 Apple 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 79 matching lines @@
         RefPtr<Element> row = children->item(index);
         HTMLElement::removeChild(row.get(), exceptionState);
     } else {
         exceptionState.throwDOMException(IndexSizeError, "The provided index (" + String::number(index) + " is outside the range [-1, " + String::number(numRows) + "].");
     }
 }
 
 int HTMLTableSectionElement::numRows() const
 {
     int rowCount = 0;
-    for (const Element* child = ElementTraversal::firstWithin(*this); child; child = ElementTraversal::nextSibling(*child)) {
-        if (child->hasTagName(trTag))
-            ++rowCount;
-    }
+    for (const HTMLTableRowElement* row = Traversal<HTMLTableRowElement>::firstChild(*this); row; row = Traversal<HTMLTableRowElement>::nextSibling(*row))
+        ++rowCount;
     return rowCount;
 }
 
 PassRefPtr<HTMLCollection> HTMLTableSectionElement::rows()
 {
     return ensureCachedHTMLCollection(TSectionRows);
 }
 
 }