Add handling to respect role attribute in AXObjects.

Source/modules/accessibility/AXListBox.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 33 matching lines @@
 
 AXListBox::~AXListBox()
 {
 }
 
 PassRefPtr<AXListBox> AXListBox::create(LayoutObject* layoutObject, AXObjectCacheImpl* axObjectCache)
 {
     return adoptRef(new AXListBox(layoutObject, axObjectCache));
 }
 
+AccessibilityRole AXListBox::roleValue() const
+{
+    AccessibilityRole ariaRole = ariaRoleAttribute();
+    if (ariaRole != UnknownRole)
+        return ariaRole;
+    return ListBoxRole;
+}
+
 } // namespace blink