Use stricter typing for HTMLCollection named getter

Source/core/html/HTMLFrameSetElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann (hausmann@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2006, 2009, 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
  * License as published by the Free Software Foundation; either
@@ skipping 201 matching lines @@
 void HTMLFrameSetElement::willRecalcStyle(StyleRecalcChange)
 {
     if (needsStyleRecalc() && renderer()) {
         renderer()->setNeedsLayout();
         clearNeedsStyleRecalc();
     }
 }
 
 DOMWindow* HTMLFrameSetElement::anonymousNamedGetter(const AtomicString& name)
 {
-    Node* frameNode = children()->namedItem(name);
-    if (!frameNode || !frameNode->hasTagName(HTMLNames::frameTag))
+    Element* frameElement = children()->namedItem(name);
+    if (!frameElement || !frameElement->hasTagName(HTMLNames::frameTag))
         return 0;
-    Document* document = toHTMLFrameElement(frameNode)->contentDocument();
+    Document* document = toHTMLFrameElement(frameElement)->contentDocument();
     if (!document || !document->frame())
         return 0;
     return document->domWindow();
 }
 
 } // namespace WebCore