Have HTMLCollection::item() return an Element as per specification

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 68 matching lines @@
     return row.release();
 }
 
 void HTMLTableSectionElement::deleteRow(int index, ExceptionState& exceptionState)
 {
     RefPtr<HTMLCollection> children = rows();
     int numRows = children ? (int)children->length() : 0;
     if (index == -1)
         index = numRows - 1;
     if (index >= 0 && index < numRows) {
-        RefPtr<Node> row = children->item(index);
+        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 rows = 0;
     const Node *n = firstChild();
@@ skipping 45 matching lines @@
 {
     setAttribute(valignAttr, value);
 }
 
 PassRefPtr<HTMLCollection> HTMLTableSectionElement::rows()
 {
     return ensureCachedHTMLCollection(TSectionRows);
 }
 
 }