Make RenderObject::style() return a const object

Source/core/rendering/RenderMenuList.h

 /*
  * This file is part of the select element renderer in WebCore.
  *
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 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.
@@ skipping 41 matching lines @@
     void didSetSelectedIndex(int listIndex);
 
     String text() const;
 
     virtual PopupMenuStyle itemStyle(unsigned listIndex) const override;
 
 private:
     HTMLSelectElement* selectElement() const;
 
     virtual bool isOfType(RenderObjectType type) const override { return type == RenderObjectMenuList || RenderFlexibleBox::isOfType(type); }
-    virtual bool isChildAllowed(RenderObject*, RenderStyle*) const override;
+    virtual bool isChildAllowed(RenderObject*, const RenderStyle*) const override;
 
     virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) override;
     virtual void removeChild(RenderObject*) override;
     virtual bool createsAnonymousWrapper() const override { return true; }
 
     virtual void updateFromElement() override;
 
     virtual LayoutRect controlClipRect(const LayoutPoint&) const override;
     virtual bool hasControlClip() const override { return true; }
     virtual bool canHaveGeneratedChildren() const override { return false; }
@@ skipping 58 matching lines @@
 
     RefPtrWillBeMember<PopupMenu> m_popup;
     bool m_popupIsVisible;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMenuList, isMenuList());
 
 }
 
 #endif