Add an accessibility role for the iframe element (re-land).

Source/core/accessibility/AXNodeObject.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 203 matching lines @@
     if (isHTMLDivElement(*node()))
         return DivRole;
     if (isHTMLParagraphElement(*node()))
         return ParagraphRole;
     if (isHTMLLabelElement(*node()))
         return LabelRole;
     if (node()->isElementNode() && toElement(node())->isFocusable())
         return GroupRole;
     if (isHTMLAnchorElement(*node()) && isClickable())
         return LinkRole;
+    if (node()->hasTagName(iframeTag))
+        return IframeRole;
 
     return UnknownRole;
 }
 
 AccessibilityRole AXNodeObject::determineAriaRoleAttribute() const
 {
     const AtomicString& ariaRole = getAttribute(roleAttr);
     if (ariaRole.isNull() || ariaRole.isEmpty())
         return UnknownRole;
 
@@ skipping 1433 matching lines @@
     float range = maxValueForRange() - minValueForRange();
     float value = valueForRange();
 
     value += range * (percentChange / 100);
     setValue(String::number(value));
 
     axObjectCache()->postNotification(node(), AXObjectCache::AXValueChanged, true);
 }
 
 } // namespace WebCore