[Slimming paint] [New Multicolumn] Repaint column rules when they change.

Source/core/rendering/style/RenderStyle.cpp

Index: Source/core/rendering/style/RenderStyle.cpp
diff --git a/Source/core/rendering/style/RenderStyle.cpp b/Source/core/rendering/style/RenderStyle.cpp
index 89cb618f6f900983e924d966eff643747b110994..972f2ff2c6600a3f9b3f97ef2e473708611e5ebe 100644
--- a/Source/core/rendering/style/RenderStyle.cpp
+++ b/Source/core/rendering/style/RenderStyle.cpp
@@ -1509,6 +1509,13 @@ void RenderStyle::resetMotionPath()
     rareNonInheritedData.access()->m_transform.access()->m_motion.m_path = nullptr;
 }
 
+bool RenderStyle::columnRuleEquivalent(const RenderStyle* otherStyle) const
+{
+    return columnRuleStyle() == otherStyle->columnRuleStyle()
+        && columnRuleWidth() == otherStyle->columnRuleWidth()
+        && visitedDependentColor(CSSPropertyWebkitColumnRuleColor) == otherStyle->visitedDependentColor(CSSPropertyWebkitColumnRuleColor);
+}
+
 TextEmphasisMark RenderStyle::textEmphasisMark() const
 {
     TextEmphasisMark mark = static_cast<TextEmphasisMark>(rareInheritedData->textEmphasisMark);