Have ElementData::attributeItem() return a reference

Source/web/WebElement.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 107 matching lines @@
     ShadowRoot* shadowRoot = constUnwrap<Element>()->shadowRoot();
     if (!shadowRoot)
         return WebNode();
     return WebNode(shadowRoot->toNode());
 }
 
 WebString WebElement::attributeLocalName(unsigned index) const
 {
     if (index >= attributeCount())
         return WebString();
-    return constUnwrap<Element>()->attributeItem(index)->localName();
+    return constUnwrap<Element>()->attributeItem(index).localName();
 }
 
 WebString WebElement::attributeValue(unsigned index) const
 {
     if (index >= attributeCount())
         return WebString();
-    return constUnwrap<Element>()->attributeItem(index)->value();
+    return constUnwrap<Element>()->attributeItem(index).value();
 }
 
 WebString WebElement::innerText()
 {
     return unwrap<Element>()->innerText();
 }
 
 WebString WebElement::computeInheritedLanguage() const
 {
     return WebString(constUnwrap<Element>()->computeInheritedLanguage());
@@ skipping 35 matching lines @@
     m_private = elem;
     return *this;
 }
 
 WebElement::operator PassRefPtr<Element>() const
 {
     return toElement(m_private.get());
 }
 
 } // namespace blink