Have StyleResolverParentPusher / SelectorFilter deal with references

Source/core/css/resolver/StyleResolver.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 165 matching lines @@
 class StyleResolver : public FontSelectorClient {
     WTF_MAKE_NONCOPYABLE(StyleResolver); WTF_MAKE_FAST_ALLOCATED;
 public:
     StyleResolver(Document&, bool matchAuthorAndUserStyles);
     ~StyleResolver();
 
     // FIXME: StyleResolver should not be keeping tree-walk state.
     // These should move to some global tree-walk state, or should be contained in a
     // TreeWalkContext or similar which is passed in to StyleResolver methods when available.
     // Using these during tree walk will allow style selector to optimize child and descendant selector lookups.
-    void pushParentElement(Element*);
-    void popParentElement(Element*);
+    void pushParentElement(Element&);
+    void popParentElement(Element&);
     void pushParentShadowRoot(const ShadowRoot&);
     void popParentShadowRoot(const ShadowRoot&);
 
     PassRefPtr<RenderStyle> styleForElement(Element*, RenderStyle* parentStyle = 0, StyleSharingBehavior = AllowStyleSharing,
         RuleMatchingBehavior = MatchAllRules, RenderRegion* regionForStyling = 0);
 
     // FIXME: The following logic related to animations and keyframes should be factored out of StyleResolver
     void resolveKeyframes(Element*, const RenderStyle*, const AtomicString& animationName, TimingFunction* defaultTimingFunction, Vector<std::pair<KeyframeAnimationEffect::KeyframeVector, RefPtr<TimingFunction> > >&);
     void keyframeStylesForAnimation(Element*, const RenderStyle*, KeyframeList&);
     const StyleRuleKeyframes* matchScopedKeyframesRule(const Element*, const StringImpl* animationName);
@@ skipping 182 matching lines @@
         PseudoId ignoreDynamicPseudo = NOPSEUDO;
         if (selectorChecker.match(selectorCheckingContext, ignoreDynamicPseudo, DOMSiblingTraversalStrategy()) == SelectorChecker::SelectorMatches)
             return true;
     }
     return false;
 }
 
 } // namespace WebCore
 
 #endif // StyleResolver_h