Introduce toHTMLInputElement(Node*), and use it.

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 1648 matching lines @@
 
     // Do the same for animations and transitions.
     style->adjustAnimations();
     style->adjustTransitions();
 
     // Important: Intrinsic margins get added to controls before the theme has adjusted the style, since the theme will
     // alter fonts and heights/widths.
     if (e && e->isFormControlElement() && style->fontSize() >= 11) {
         // Don't apply intrinsic margins to image buttons. The designer knows how big the images are,
         // so we have to treat all image buttons as though they were explicitly sized.
-        if (!e->hasTagName(inputTag) || !static_cast<HTMLInputElement*>(e)->isImageButton())
+        if (!e->hasTagName(inputTag) || !toHTMLInputElement(e)->isImageButton())
             addIntrinsicMargins(style);
     }
 
     // Let the theme also have a crack at adjusting the style.
     if (style->hasAppearance())
         RenderTheme::defaultTheme()->adjustStyle(this, style, e, m_state.hasUAAppearance(), m_state.borderData(), m_state.backgroundData(), m_state.backgroundColor());
 
     // If we have first-letter pseudo style, do not share this style.
     if (style->hasPseudoStyle(FIRST_LETTER))
         style->setUnique();
@@ skipping 2057 matching lines @@
     info.addMember(m_state, "state");
 
     // FIXME: move this to a place where it would be called only once?
     info.addMember(CSSDefaultStyleSheets::defaultStyle, "defaultStyle");
     info.addMember(CSSDefaultStyleSheets::defaultQuirksStyle, "defaultQuirksStyle");
     info.addMember(CSSDefaultStyleSheets::defaultPrintStyle, "defaultPrintStyle");
     info.addMember(CSSDefaultStyleSheets::defaultViewSourceStyle, "defaultViewSourceStyle");
 }
 
 } // namespace WebCore