Make RenderObject::style() return a const object

Source/core/css/resolver/ElementResolveContext.h

Index: Source/core/css/resolver/ElementResolveContext.h
diff --git a/Source/core/css/resolver/ElementResolveContext.h b/Source/core/css/resolver/ElementResolveContext.h
index ae15df57d802745a05566742ccd5a335d8b45d6a..d1138c859455c1123af35b97c684f517c5a7969a 100644
--- a/Source/core/css/resolver/ElementResolveContext.h
+++ b/Source/core/css/resolver/ElementResolveContext.h
@@ -43,14 +43,14 @@ public:
     Element* element() const { return m_element; }
     const ContainerNode* parentNode() const { return m_parentNode; }
     const RenderStyle* rootElementStyle() const { return m_rootElementStyle; }
-    RenderStyle* parentStyle() const { return parentNode() ? parentNode()->renderStyle() : nullptr; }
+    const RenderStyle* parentStyle() const { return parentNode() ? parentNode()->renderStyle() : nullptr; }
     EInsideLink elementLinkState() const { return m_elementLinkState; }
     bool distributedToInsertionPoint() const { return m_distributedToInsertionPoint; }
 
 private:
     RawPtrWillBeMember<Element> m_element;
     RawPtrWillBeMember<ContainerNode> m_parentNode;
-    RenderStyle* m_rootElementStyle;
+    const RenderStyle* m_rootElementStyle;
     EInsideLink m_elementLinkState;
     bool m_distributedToInsertionPoint;
 };