Make RenderObject::style() return a const object

Source/core/paint/InlineFlowBoxPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef InlineFlowBoxPainter_h
 #define InlineFlowBoxPainter_h
 
 #include "core/rendering/style/ShadowData.h"
 #include "platform/graphics/GraphicsTypes.h"
 #include "platform/text/TextDirection.h"
@@ skipping 13 matching lines @@
 class InlineFlowBoxPainter {
 public:
     InlineFlowBoxPainter(InlineFlowBox& inlineFlowBox) : m_inlineFlowBox(inlineFlowBox) { }
     void paint(const PaintInfo&, const LayoutPoint&, const LayoutUnit lineTop, const LayoutUnit lineBottom);
 
 private:
     void paintBoxDecorationBackground(const PaintInfo&, const LayoutPoint&);
     void paintMask(const PaintInfo&, const LayoutPoint&);
     void paintFillLayers(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, SkXfermode::Mode = SkXfermode::kSrcOver_Mode);
     void paintFillLayer(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, SkXfermode::Mode);
-    void paintBoxShadow(const PaintInfo&, RenderStyle*, ShadowStyle, const LayoutRect&);
+    void paintBoxShadow(const PaintInfo&, const RenderStyle*, ShadowStyle, const LayoutRect&);
     LayoutRect roundedFrameRectClampedToLineTopAndBottomIfNeeded() const;
     LayoutRect paintRectForImageStrip(const LayoutPoint&, const LayoutSize&, TextDirection) const;
 
     InlineFlowBox& m_inlineFlowBox;
 };
 
 } // namespace blink
 
 #endif // InlineFlowBoxPainter_h