Make RenderObject::style() return a const object

Source/core/layout/LayoutTheme.h

Index: Source/core/layout/LayoutTheme.h
diff --git a/Source/core/layout/LayoutTheme.h b/Source/core/layout/LayoutTheme.h
index 61b01dc15c48a5737b08d3770102509f220da262..074c95de66e048aaf9116743f19621f31665d1d1 100644
--- a/Source/core/layout/LayoutTheme.h
+++ b/Source/core/layout/LayoutTheme.h
@@ -142,14 +142,14 @@ public:
     void systemFont(CSSValueID systemFontID, FontDescription&);
     virtual Color systemColor(CSSValueID) const;
 
-    virtual int minimumMenuListSize(RenderStyle*) const { return 0; }
+    virtual int minimumMenuListSize(const RenderStyle*) const { return 0; }
 
     virtual void adjustSliderThumbSize(RenderStyle*, Element*) const;
 
-    virtual int popupInternalPaddingLeft(RenderStyle*) const { return 0; }
-    virtual int popupInternalPaddingRight(RenderStyle*) const { return 0; }
-    virtual int popupInternalPaddingTop(RenderStyle*) const { return 0; }
-    virtual int popupInternalPaddingBottom(RenderStyle*) const { return 0; }
+    virtual int popupInternalPaddingLeft(const RenderStyle*) const { return 0; }
+    virtual int popupInternalPaddingRight(const RenderStyle*) const { return 0; }
+    virtual int popupInternalPaddingTop(const RenderStyle*) const { return 0; }
+    virtual int popupInternalPaddingBottom(const RenderStyle*) const { return 0; }
     virtual bool popupOptionSupportsTextIndent() const { return false; }
 
     virtual ScrollbarControlSize scrollbarControlSizeForPart(ControlPart) { return RegularScrollbar; }
@@ -274,7 +274,7 @@ protected:
     virtual bool paintMediaFullScreenVolumeSliderTrack(RenderObject*, const PaintInfo&, const IntRect&) { return true; }
     virtual bool paintMediaFullScreenVolumeSliderThumb(RenderObject*, const PaintInfo&, const IntRect&) { return true; }
 
-    virtual bool shouldUseFallbackTheme(RenderStyle*) const;
+    virtual bool shouldUseFallbackTheme(const RenderStyle*) const;
     void adjustStyleUsingFallbackTheme(RenderStyle*, Element*);
     bool paintUsingFallbackTheme(RenderObject*, const PaintInfo&, const IntRect&);
     void adjustCheckboxStyleUsingFallbackTheme(RenderStyle*, Element*) const;