Make RenderObject::style() return a const object

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003-2011, 2013, 2014 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
@@ skipping 596 matching lines @@
 #ifndef NDEBUG
     virtual void formatForDebugger(char* buffer, unsigned length) const override;
 #endif
 
     bool pseudoStyleCacheIsInvalid(const LayoutStyle* currentStyle, LayoutStyle* newStyle);
 
     void cancelFocusAppearanceUpdate();
 
     virtual LayoutStyle* virtualComputedStyle(PseudoId pseudoElementSpecifier = NOPSEUDO) override { return computedStyle(pseudoElementSpecifier); }
 
-    inline void updateCallbackSelectors(LayoutStyle* oldStyle, LayoutStyle* newStyle);
+    inline void updateCallbackSelectors(const LayoutStyle* oldStyle, const LayoutStyle* newStyle);
     inline void removeCallbackSelectors();
     inline void addCallbackSelectors();
 
     // cloneNode is private so that non-virtual cloneElementWithChildren and cloneElementWithoutChildren
     // are used instead.
     virtual PassRefPtrWillBeRawPtr<Node> cloneNode(bool deep) override;
     virtual PassRefPtrWillBeRawPtr<Element> cloneElementWithoutAttributesAndChildren();
 
     QualifiedName m_tagName;
 
@@ skipping 251 matching lines @@
     static PassRefPtrWillBeRawPtr<T> create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     PassRefPtrWillBeRawPtr<T> T::create(const QualifiedName& tagName, Document& document) \
     { \
         return adoptRefWillBeNoop(new T(tagName, document)); \
     }
 
 } // namespace
 
 #endif // Element_h