Make RenderObject::style() return a const object

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index dc781e7f08c08a67a0f47969407a83e82a7e6146..a6d1dfcabad606ebc7650413945f21ea6006f291 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -310,7 +310,7 @@ public:
 
     virtual void attach(const AttachContext& = AttachContext()) override;
     virtual void detach(const AttachContext& = AttachContext()) override;
-    virtual RenderObject* createRenderer(RenderStyle*);
+    virtual RenderObject* createRenderer(const RenderStyle*);
     virtual bool rendererIsNeeded(const RenderStyle&);
     void recalcStyle(StyleRecalcChange, Text* nextTextSibling = nullptr);
     void pseudoStateChanged(CSSSelector::PseudoType);
@@ -613,7 +613,7 @@ private:
 
     virtual RenderStyle* virtualComputedStyle(PseudoId pseudoElementSpecifier = NOPSEUDO) override { return computedStyle(pseudoElementSpecifier); }
 
-    inline void updateCallbackSelectors(RenderStyle* oldStyle, RenderStyle* newStyle);
+    inline void updateCallbackSelectors(const RenderStyle* oldStyle, const RenderStyle* newStyle);
     inline void removeCallbackSelectors();
     inline void addCallbackSelectors();