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

Source/core/rendering/RenderMultiColumnFlowThread.cpp

Index: Source/core/rendering/RenderMultiColumnFlowThread.cpp
diff --git a/Source/core/rendering/RenderMultiColumnFlowThread.cpp b/Source/core/rendering/RenderMultiColumnFlowThread.cpp
index 3fcf0db63513c843ae6c22dc48c08d79324a6d2d..44a0e9b5e919e7db2bc00a5abcc450acad708868 100644
--- a/Source/core/rendering/RenderMultiColumnFlowThread.cpp
+++ b/Source/core/rendering/RenderMultiColumnFlowThread.cpp
@@ -216,6 +216,12 @@ bool RenderMultiColumnFlowThread::recalculateColumnHeights()
     return needsRelayout;
 }
 
+void RenderMultiColumnFlowThread::columnRuleStyleDidChange()
+{
+    for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet())
+        columnSet->setShouldDoFullPaintInvalidation(PaintInvalidationStyleChange);
+}
+
 void RenderMultiColumnFlowThread::calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const
 {
     RenderBlock* columnBlock = multiColumnBlockFlow();