Add iterator object to iterate efficiently over an Element's attributes

Source/core/xml/XPathStep.cpp

 /*
  * Copyright (C) 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * 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
@@ skipping 342 matching lines @@
                 if (n && n->namespaceURI() != XMLNSNames::xmlnsNamespaceURI) { // In XPath land, namespace nodes are not accessible on the attribute axis.
                     if (nodeMatches(n.get(), AttributeAxis, nodeTest())) // Still need to check merged predicates.
                         nodes.append(n.release());
                 }
                 return;
             }
 
             if (!contextElement->hasAttributes())
                 return;
 
-            unsigned attributeCount = contextElement->attributeCount();
-            for (unsigned i = 0; i < attributeCount; ++i) {
-                RefPtrWillBeRawPtr<Attr> attr = contextElement->ensureAttr(contextElement->attributeItem(i).name());
+            AttributeIteratorAccessor attributes = contextElement->attributesIterator();
+            AttributeConstIterator end = attributes.end();
+            for (AttributeConstIterator it = attributes.begin(); it != end; ++it) {
+                RefPtrWillBeRawPtr<Attr> attr = contextElement->ensureAttr(it->name());
                 if (nodeMatches(attr.get(), AttributeAxis, nodeTest()))
                     nodes.append(attr.release());
             }
             return;
         }
         case NamespaceAxis:
             // XPath namespace nodes are not implemented.
             return;
         case SelfAxis:
             if (nodeMatches(context, SelfAxis, nodeTest()))
@@ skipping 26 matching lines @@
             nodes.markSorted(false);
             return;
         }
     }
     ASSERT_NOT_REACHED();
 }
 
 
 }
 }