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

Source/core/rendering/RenderFileUploadControl.cpp

 /*
  * Copyright (C) 2006, 2007, 2012 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
  * 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
@@ skipping 188 matching lines @@
 PositionWithAffinity RenderFileUploadControl::positionForPoint(const LayoutPoint&)
 {
     return PositionWithAffinity();
 }
 
 HTMLInputElement* RenderFileUploadControl::uploadButton() const
 {
     // FIXME: This should be on HTMLInputElement as an API like innerButtonElement().
     HTMLInputElement* input = toHTMLInputElement(node());
     Node* buttonNode = input->userAgentShadowRoot()->firstChild();
-    return buttonNode && buttonNode->isHTMLElement() && buttonNode->hasTagName(inputTag) ? toHTMLInputElement(buttonNode) : 0;
+    return isHTMLInputElement(buttonNode) ? toHTMLInputElement(buttonNode) : 0;
 }
 
 String RenderFileUploadControl::buttonValue()
 {
     if (HTMLInputElement* button = uploadButton())
         return button->value();
 
     return String();
 }
 
 String RenderFileUploadControl::fileTextValue() const
 {
     HTMLInputElement* input = toHTMLInputElement(node());
     ASSERT(input->files());
     return RenderTheme::theme().fileListNameForWidth(input->locale(), input->files(), style()->font(), maxFilenameWidth());
 }
 
 } // namespace WebCore