Make RenderObject::style() return a const object

Source/core/animation/css/CSSAnimations.h

Index: Source/core/animation/css/CSSAnimations.h
diff --git a/Source/core/animation/css/CSSAnimations.h b/Source/core/animation/css/CSSAnimations.h
index 48baebd83e27648086a3078734ad7cfbec3b9226..225c720f2e2e7b8e258a0c90514a25dcba449b33 100644
--- a/Source/core/animation/css/CSSAnimations.h
+++ b/Source/core/animation/css/CSSAnimations.h
@@ -60,7 +60,7 @@ public:
 
     static const StylePropertyShorthand& animatableProperties();
     static bool isAllowedAnimation(CSSPropertyID);
-    static PassOwnPtrWillBeRawPtr<CSSAnimationUpdate> calculateUpdate(const Element* animatingElement, Element&, const LayoutStyle&, LayoutStyle* parentStyle, StyleResolver*);
+    static PassOwnPtrWillBeRawPtr<CSSAnimationUpdate> calculateUpdate(const Element* animatingElement, Element&, const LayoutStyle&, const LayoutStyle* parentStyle, StyleResolver*);
 
     void setPendingUpdate(PassOwnPtrWillBeRawPtr<CSSAnimationUpdate> update) { m_pendingUpdate = update; }
     void maybeApplyPendingUpdate(Element*);
@@ -124,7 +124,7 @@ private:
 
     WillBeHeapHashMap<CSSPropertyID, RefPtrWillBeMember<Interpolation>> m_previousActiveInterpolationsForAnimations;
 
-    static void calculateAnimationUpdate(CSSAnimationUpdate*, const Element* animatingElement, Element&, const LayoutStyle&, LayoutStyle* parentStyle, StyleResolver*);
+    static void calculateAnimationUpdate(CSSAnimationUpdate*, const Element* animatingElement, Element&, const LayoutStyle&, const LayoutStyle* parentStyle, StyleResolver*);
     static void calculateTransitionUpdate(CSSAnimationUpdate*, const Element* animatingElement, const LayoutStyle&);
     static void calculateTransitionUpdateForProperty(CSSPropertyID, CSSPropertyID eventId, const CSSTransitionData&, size_t transitionIndex, const LayoutStyle& oldStyle, const LayoutStyle&, const TransitionMap* activeTransitions, CSSAnimationUpdate*, const Element*);