Make it obvious an HTMLFormControlsCollection can only contain HTMLElements

Source/core/html/HTMLFormControlsCollection.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef HTMLFormControlsCollection_h
 #define HTMLFormControlsCollection_h
 
 #include "core/html/FormAssociatedElement.h"
 #include "core/html/HTMLCollection.h"
+#include "core/html/HTMLElement.h"
 #include "core/html/RadioNodeList.h"
 
 namespace blink {
 
-class HTMLElement;
 class HTMLImageElement;
 class QualifiedName;
 
 // This class is just a big hack to find form elements even in malformed HTML elements.
 // The famous <table><tr><form><td> problem.
 
 class HTMLFormControlsCollection FINAL : public HTMLCollection {
 public:
     static PassRefPtrWillBeRawPtr<HTMLFormControlsCollection> create(ContainerNode&, CollectionType);
 
     virtual ~HTMLFormControlsCollection();
 
-    virtual Element* namedItem(const AtomicString& name) const OVERRIDE;
+    HTMLElement* item(unsigned offset) const { return toHTMLElement(HTMLCollection::item(offset)); }
+
+    virtual HTMLElement* namedItem(const AtomicString& name) const OVERRIDE;
     void namedGetter(const AtomicString& name, RefPtrWillBeRawPtr<RadioNodeList>&, RefPtrWillBeRawPtr<Element>&);
 
     virtual void trace(Visitor*) OVERRIDE;
 
 private:
     explicit HTMLFormControlsCollection(ContainerNode&);
 
     virtual void updateIdNameCache() const OVERRIDE;
     virtual void supportedPropertyNames(Vector<String>& names) OVERRIDE;
 
     const FormAssociatedElement::List& formControlElements() const;
     const WillBeHeapVector<RawPtrWillBeMember<HTMLImageElement> >& formImageElements() const;
-    virtual Element* virtualItemAfter(Element*) const OVERRIDE;
+    virtual HTMLElement* virtualItemAfter(Element*) const OVERRIDE;
     virtual void invalidateCache(Document* oldDocument = 0) const OVERRIDE;
 
-    mutable RawPtrWillBeMember<Element> m_cachedElement;
+    mutable RawPtrWillBeMember<HTMLElement> m_cachedElement;
     mutable unsigned m_cachedElementOffsetInArray;
 };
 DEFINE_TYPE_CASTS(HTMLFormControlsCollection, LiveNodeListBase, collection, collection->type() == FormControls, collection.type() == FormControls);
 
 } // namespace
 
 #endif