Make it clear a DocumentNameCollection can only contain HTMLElements

Source/core/html/DocumentNameCollection.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/html/DocumentNameCollection.h"
 
 #include "core/html/HTMLEmbedElement.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLObjectElement.h"
 
 namespace blink {
 
 DocumentNameCollection::DocumentNameCollection(ContainerNode& document, const AtomicString& name)
     : HTMLNameCollection(document, DocumentNamedItems, name)
 {
 }
 
-bool DocumentNameCollection::elementMatches(const Element& element) const
+bool DocumentNameCollection::elementMatches(const HTMLElement& element) const
 {
     // Match images, forms, applets, embeds, objects and iframes by name,
     // applets and object by id, and images by id but only if they have
     // a name attribute (this very strange rule matches IE)
     if (isHTMLFormElement(element) || isHTMLIFrameElement(element) || (isHTMLEmbedElement(element) && toHTMLEmbedElement(element).isExposed()))
         return element.getNameAttribute() == m_name;
     if (isHTMLAppletElement(element) || (isHTMLObjectElement(element) && toHTMLObjectElement(element).isExposed()))
         return element.getNameAttribute() == m_name || element.getIdAttribute() == m_name;
     if (isHTMLImageElement(element))
         return element.getNameAttribute() == m_name || (element.getIdAttribute() == m_name && element.hasName());
     return false;
 }
 
 } // namespace blink