Inherit Presentation role only when elements without a explicit role defined.

Source/modules/accessibility/AXRenderObject.cpp

 /*
 * Copyright (C) 2008 Apple 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 2348 matching lines @@
 
     AXObject* parent = parentObject();
     if (!parent->isAXRenderObject())
         return false;
 
     Node* elementNode = toAXRenderObject(parent)->node();
     if (!elementNode || !elementNode->isElementNode())
         return false;
 
     QualifiedName tagName = toElement(elementNode)->tagQName();
-    if (tagName == ulTag || tagName == olTag || tagName == dlTag)
-        return (parent->roleValue() == NoneRole || parent->roleValue() == PresentationalRole);
+    if (tagName != ulTag && tagName != olTag && tagName != dlTag)
+        return false;
+
+    if (parent->roleValue() == NoneRole || parent->roleValue() == PresentationalRole)
+        return ariaRoleAttribute() == UnknownRole;
 
     return false;
 }
 
 LayoutRect AXRenderObject::computeElementRect() const
 {
     RenderObject* obj = m_renderer;
 
     if (!obj)
         return LayoutRect();
@@ skipping 35 matching lines @@
         if (label && label->renderer()) {
             LayoutRect labelRect = axObjectCache()->getOrCreate(label)->elementRect();
             result.unite(labelRect);
         }
     }
 
     return result;
 }
 
 } // namespace blink