Make RenderObject::style() return a const object

Source/core/html/shadow/ProgressShadowElement.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 37 matching lines @@
     virtual bool rendererIsNeeded(const RenderStyle&) override;
 };
 
 class ProgressInnerElement final : public ProgressShadowElement {
 public:
     DECLARE_NODE_FACTORY(ProgressInnerElement);
 
 private:
     explicit ProgressInnerElement(Document&);
 
-    virtual RenderObject* createRenderer(RenderStyle*) override;
+    virtual RenderObject* createRenderer(const RenderStyle*) override;
     virtual bool rendererIsNeeded(const RenderStyle&) override;
 };
 
 class ProgressBarElement final : public ProgressShadowElement {
 public:
     DECLARE_NODE_FACTORY(ProgressBarElement);
 
 private:
     explicit ProgressBarElement(Document&);
 };
 
 class ProgressValueElement final : public ProgressShadowElement {
 public:
     DECLARE_NODE_FACTORY(ProgressValueElement);
     void setWidthPercentage(double);
 
 private:
     explicit ProgressValueElement(Document&);
 };
 
 }
 
 #endif // ProgressShadowElement_h