Use new is*Element() helper functions more in web/ code

Source/web/WebInputElement.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 197 matching lines @@
     return *this;
 }
 
 WebInputElement::operator PassRefPtr<HTMLInputElement>() const
 {
     return toHTMLInputElement(m_private.get());
 }
 
 WebInputElement* toWebInputElement(WebElement* webElement)
 {
-    if (!webElement->unwrap<Element>()->hasTagName(HTMLNames::inputTag))
+    if (!isHTMLInputElement(*webElement->unwrap<Element>()))
         return 0;
 
     return static_cast<WebInputElement*>(webElement);
 }
 } // namespace blink