Have ElementTraversal / NodeTraversal's next() methods take a reference

Source/core/css/StyleInvalidationAnalysis.cpp

 /*
  * Copyright (C) 2012 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 205 matching lines @@
     if (m_idScopes.isEmpty() && m_classScopes.isEmpty())
         return;
     Element* element = ElementTraversal::firstWithin(document);
     while (element) {
         if (elementMatchesSelectorScopes(element, m_idScopes, m_classScopes)) {
             element->setNeedsStyleRecalc();
             // The whole subtree is now invalidated, we can skip to the next sibling.
             element = ElementTraversal::nextSkippingChildren(element);
             continue;
         }
-        element = ElementTraversal::next(element);
+        element = ElementTraversal::next(*element);
     }
 }
 
 }