Support aria-dropeffect attribute.

Source/web/WebAXObject.cpp

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 459 matching lines @@
     m_private->ariaDescribedbyElements(describedby);
 
     WebVector<WebAXObject> result(describedby.size());
     for (size_t i = 0; i < describedby.size(); i++)
         result[i] = WebAXObject(describedby[i]);
     describedbyElements.swap(result);
 
     return true;
 }
 
+WebString WebAXObject::ariaDropEffect() const
+{
+    if (isDetached())
+        return WebString();
+
+    return WebString(m_private->ariaDropEffect());
+}
+
 bool WebAXObject::ariaHasPopup() const
 {
     if (isDetached())
         return false;
 
     return m_private->ariaHasPopup();
 }
 
 bool WebAXObject::ariaFlowTo(WebVector<WebAXObject>& flowToElements) const
 {
@@ skipping 821 matching lines @@
     m_private = object;
     return *this;
 }
 
 WebAXObject::operator WTF::PassRefPtr<AXObject>() const
 {
     return m_private.get();
 }
 
 } // namespace blink