Introduce toHTMLInputElement(Node*), and use it.

Source/core/html/HTMLFormElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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 292 matching lines @@
 }
 
 void HTMLFormElement::getTextFieldValues(StringPairVector& fieldNamesAndValues) const
 {
     ASSERT_ARG(fieldNamesAndValues, fieldNamesAndValues.isEmpty());
 
     fieldNamesAndValues.reserveCapacity(m_associatedElements.size());
     for (unsigned i = 0; i < m_associatedElements.size(); ++i) {
         FormAssociatedElement* control = m_associatedElements[i];
         HTMLElement* element = toHTMLElement(control);
-        if (!element->hasLocalName(inputTag))
+        if (!element->hasTagName(inputTag))
             continue;
 
-        HTMLInputElement* input = static_cast<HTMLInputElement*>(control);
+        HTMLInputElement* input = toHTMLInputElement(element);
         if (!input->isTextField())
             continue;
 
         fieldNamesAndValues.append(make_pair(input->name().string(), input->value()));
     }
 }
 
 void HTMLFormElement::submit(Event* event, bool activateSubmitButton, bool processingUserGesture, FormSubmissionTrigger formSubmissionTrigger)
 {
     FrameView* view = document()->view();
@@ skipping 403 matching lines @@
         returnValue1Enabled = true;
         returnValue1 = elements.at(0);
         return;
     }
 
     returnValue0Enabled = true;
     returnValue0 = NamedNodesCollection::create(elements);
 }
 
 } // namespace