Introduce toHTMLFormControlElement, and use it.

Source/core/accessibility/AccessibilityNodeObject.cpp

 /*
 * Copyright (C) 2012, 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:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 686 matching lines @@
     return !node->rendererIsEditable();
 }
 
 bool AccessibilityNodeObject::isRequired() const
 {
     if (equalIgnoringCase(getAttribute(aria_requiredAttr), "true"))
         return true;
 
     Node* n = this->node();
     if (n && (n->isElementNode() && toElement(n)->isFormControlElement()))
-        return static_cast<HTMLFormControlElement*>(n)->isRequired();
+        return toHTMLFormControlElement(n)->isRequired();
 
     return false;
 }
 
 bool AccessibilityNodeObject::canSetFocusAttribute() const
 {
     Node* node = this->node();
     if (!node)
         return false;
 
@@ skipping 908 matching lines @@
         useTextUnderElement = true;
 
     if (useTextUnderElement) {
         String text = textUnderElement();
         if (!text.isEmpty())
             textOrder.append(AccessibilityText(text, ChildrenText));
     }
 }
 
 } // namespace WebCore