Make RenderObject::style() return a const object

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 85 matching lines @@
     explicit StyleResolver(Document&);
     virtual ~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&);
 
-    PassRefPtr<LayoutStyle> styleForElement(Element*, LayoutStyle* parentStyle = 0, StyleSharingBehavior = AllowStyleSharing,
+    PassRefPtr<LayoutStyle> styleForElement(Element*, const LayoutStyle* parentStyle = 0, StyleSharingBehavior = AllowStyleSharing,
         RuleMatchingBehavior = MatchAllRules);
 
-    PassRefPtr<LayoutStyle> styleForKeyframe(Element&, const LayoutStyle&, LayoutStyle* parentStyle, const StyleRuleKeyframe*, const AtomicString& animationName);
+    PassRefPtr<LayoutStyle> styleForKeyframe(Element&, const LayoutStyle&, const LayoutStyle* parentStyle, const StyleRuleKeyframe*, const AtomicString& animationName);
     static PassRefPtrWillBeRawPtr<AnimatableValue> createAnimatableValueSnapshot(Element&, CSSPropertyID, CSSValue&);
     static PassRefPtrWillBeRawPtr<AnimatableValue> createAnimatableValueSnapshot(StyleResolverState&, CSSPropertyID, CSSValue&);
 
-    PassRefPtr<LayoutStyle> pseudoStyleForElement(Element*, const PseudoStyleRequest&, LayoutStyle* parentStyle);
+    PassRefPtr<LayoutStyle> pseudoStyleForElement(Element*, const PseudoStyleRequest&, const LayoutStyle* parentStyle);
 
     PassRefPtr<LayoutStyle> styleForPage(int pageIndex);
     PassRefPtr<LayoutStyle> defaultStyleForElement();
     PassRefPtr<LayoutStyle> styleForText(Text*);
 
     static PassRefPtr<LayoutStyle> styleForDocument(Document&);
 
     // FIXME: It could be better to call appendAuthorStyleSheets() directly after we factor StyleResolver further.
     // https://bugs.webkit.org/show_bug.cgi?id=108890
     void appendAuthorStyleSheets(const WillBeHeapVector<RefPtrWillBeMember<CSSStyleSheet> >&);
@@ skipping 114 matching lines @@
 
     void matchPageRules(MatchResult&, RuleSet*, bool isLeftPage, bool isFirstPage, const String& pageName);
     void matchPageRulesForList(WillBeHeapVector<RawPtrWillBeMember<StyleRulePage> >& matchedRules, const WillBeHeapVector<RawPtrWillBeMember<StyleRulePage> >&, bool isLeftPage, bool isFirstPage, const String& pageName);
     void collectViewportRules();
 
     bool isLeftPage(int pageIndex) const;
     bool isRightPage(int pageIndex) const { return !isLeftPage(pageIndex); }
     bool isFirstPage(int pageIndex) const;
     String pageName(int pageIndex) const;
 
-    bool pseudoStyleForElementInternal(Element&, const PseudoStyleRequest&, LayoutStyle* parentStyle, StyleResolverState&);
+    bool pseudoStyleForElementInternal(Element&, const PseudoStyleRequest&, const LayoutStyle* parentStyle, StyleResolverState&);
 
     PassRefPtrWillBeRawPtr<PseudoElement> createPseudoElement(Element* parent, PseudoId);
 
     Document& document() { return *m_document; }
 
     static LayoutStyle* s_styleNotYetAvailable;
 
     void cacheBorderAndBackground();
 
     MatchedPropertiesCache m_matchedPropertiesCache;
@@ skipping 28 matching lines @@
     OwnPtr<StyleResolverStats> m_styleResolverStatsTotals;
     unsigned m_styleResolverStatsSequence;
 
     // Use only for Internals::updateStyleAndReturnAffectedElementCount.
     unsigned m_accessCount;
 };
 
 } // namespace blink
 
 #endif // StyleResolver_h