Make RenderObject::style() return a const object

Source/core/rendering/style/RenderStyle.h

Index: Source/core/rendering/style/RenderStyle.h
diff --git a/Source/core/rendering/style/RenderStyle.h b/Source/core/rendering/style/RenderStyle.h
index cd4d83ee04c09f840422195a969b7300f6013f50..2d6be261b436255152437ec27fecd0425def9ad3 100644
--- a/Source/core/rendering/style/RenderStyle.h
+++ b/Source/core/rendering/style/RenderStyle.h
@@ -258,8 +258,9 @@ protected:
 
         unsigned styleType : 6; // PseudoId
         unsigned pseudoBits : 8;
-        unsigned explicitInheritance : 1; // Explicitly inherits a non-inherited property
-        unsigned unique : 1; // Style can not be shared.
+        // FIXME: This should be moved to ElementRateData.
+        mutable unsigned explicitInheritance : 1; // Explicitly inherits a non-inherited property
+        mutable unsigned unique : 1; // Style can not be shared.
 
         unsigned emptyState : 1;
 
@@ -884,12 +885,12 @@ public:
     bool hasCurrentOpacityAnimation() const { return rareNonInheritedData->m_hasCurrentOpacityAnimation; }
     bool hasCurrentTransformAnimation() const { return rareNonInheritedData->m_hasCurrentTransformAnimation; }
     bool hasCurrentFilterAnimation() const { return rareNonInheritedData->m_hasCurrentFilterAnimation; }
-    bool shouldCompositeForCurrentAnimations() { return hasCurrentOpacityAnimation() || hasCurrentTransformAnimation() || hasCurrentFilterAnimation(); }
+    bool shouldCompositeForCurrentAnimations() const { return hasCurrentOpacityAnimation() || hasCurrentTransformAnimation() || hasCurrentFilterAnimation(); }
 
     bool isRunningOpacityAnimationOnCompositor() const { return rareNonInheritedData->m_runningOpacityAnimationOnCompositor; }
     bool isRunningTransformAnimationOnCompositor() const { return rareNonInheritedData->m_runningTransformAnimationOnCompositor; }
     bool isRunningFilterAnimationOnCompositor() const { return rareNonInheritedData->m_runningFilterAnimationOnCompositor; }
-    bool isRunningAnimationOnCompositor() { return isRunningOpacityAnimationOnCompositor() || isRunningTransformAnimationOnCompositor() || isRunningFilterAnimationOnCompositor(); }
+    bool isRunningAnimationOnCompositor() const { return isRunningOpacityAnimationOnCompositor() || isRunningTransformAnimationOnCompositor() || isRunningFilterAnimationOnCompositor(); }
 
     LineBoxContain lineBoxContain() const { return rareInheritedData->m_lineBoxContain; }
     const LineClampValue& lineClamp() const { return rareNonInheritedData->lineClamp; }
@@ -1276,7 +1277,7 @@ public:
     // For valid values of column-break-inside see http://www.w3.org/TR/css3-multicol/#break-before-break-after-break-inside
     void setColumnBreakInside(EPageBreak p) { ASSERT(p == PBAUTO || p == PBAVOID); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakInside, p); }
     void setColumnBreakAfter(EPageBreak p) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakAfter, p); }
-    void inheritColumnPropertiesFrom(RenderStyle* parent) { rareNonInheritedData.access()->m_multiCol = parent->rareNonInheritedData->m_multiCol; }
+    void inheritColumnPropertiesFrom(const RenderStyle& parent) { rareNonInheritedData.access()->m_multiCol = parent.rareNonInheritedData->m_multiCol; }
     void setHasInlineTransform(bool b) { SET_VAR(rareNonInheritedData, m_hasInlineTransform, b); }
     void setTransform(const TransformOperations& ops) { SET_VAR(rareNonInheritedData.access()->m_transform, m_operations, ops); }
     void setTransformOriginX(const Length& v) { setTransformOrigin(TransformOrigin(v, transformOriginY(), transformOriginZ())); }
@@ -1455,7 +1456,7 @@ public:
 
     // A unique style is one that has matches something that makes it impossible to share.
     bool unique() const { return noninherited_flags.unique; }
-    void setUnique() { noninherited_flags.unique = true; }
+    void setUnique() const { noninherited_flags.unique = true; }
 
     bool isSharable() const;
 
@@ -1464,7 +1465,7 @@ public:
 
     Color visitedDependentColor(int colorProperty) const;
 
-    void setHasExplicitlyInheritedProperties() { noninherited_flags.explicitInheritance = true; }
+    void setHasExplicitlyInheritedProperties() const { noninherited_flags.explicitInheritance = true; }
     bool hasExplicitlyInheritedProperties() const { return noninherited_flags.explicitInheritance; }
 
     bool hasBoxDecorations() const { return hasBorder() || hasBorderRadius() || hasOutline() || hasAppearance() || boxShadow() || hasFilter() || resize() != RESIZE_NONE; }