Consistently use ElementTraversal API when looking for an Element

Source/core/html/HTMLTableSectionElement.cpp

Index: Source/core/html/HTMLTableSectionElement.cpp
diff --git a/Source/core/html/HTMLTableSectionElement.cpp b/Source/core/html/HTMLTableSectionElement.cpp
index bf796d6ef31bfb3c654b4259965ecba9034fe4da..31a0f3ee7dbfcf68f3ae766b237d619fa5dd159b 100644
--- a/Source/core/html/HTMLTableSectionElement.cpp
+++ b/Source/core/html/HTMLTableSectionElement.cpp
@@ -27,6 +27,7 @@
 
 #include "HTMLNames.h"
 #include "bindings/v8/ExceptionState.h"
+#include "core/dom/ElementTraversal.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/html/HTMLCollection.h"
 #include "core/html/HTMLTableElement.h"
@@ -95,15 +96,12 @@ void HTMLTableSectionElement::deleteRow(int index, ExceptionState& exceptionStat
 
 int HTMLTableSectionElement::numRows() const
 {
-    int rows = 0;
-    const Node *n = firstChild();
-    while (n) {
-        if (n->hasTagName(trTag))
-            rows++;
-        n = n->nextSibling();
+    int rowCount = 0;
+    for (const Element* child = ElementTraversal::firstWithin(*this); child; child = ElementTraversal::nextSibling(*child)) {
+        if (child->hasTagName(trTag))
+            ++rowCount;
     }
-
-    return rows;
+    return rowCount;
 }
 
 PassRefPtr<HTMLCollection> HTMLTableSectionElement::rows()