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

Source/core/rendering/RenderMultiColumnFlowThread.h

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 134 matching lines @@
 
     virtual LayoutSize columnOffset(const LayoutPoint&) const override final;
 
     // Do we need to set a new width and lay out?
     virtual bool needsNewWidth() const;
 
     void layoutColumns(bool relayoutChildren, SubtreeLayoutScope&);
 
     bool recalculateColumnHeights();
 
+    void columnRuleStyleDidChange();
+
 protected:
     RenderMultiColumnFlowThread();
     void setProgressionIsInline(bool isInline) { m_progressionIsInline = isInline; }
 
     virtual void layout() override;
 
 private:
     void calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const;
     void createAndInsertMultiColumnSet();
     void createAndInsertSpannerPlaceholder(RenderBox* spanner);
@@ skipping 16 matching lines @@
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
     bool m_inBalancingPass; // Set when relayouting for column balancing.
     bool m_needsColumnHeightsRecalculation; // Set when we need to recalculate the column set heights after layout.
     bool m_progressionIsInline; // Always true for regular multicol. False for paged-y overflow.
     bool m_isBeingEvacuated;
 };
 
 } // namespace blink
 
 #endif // RenderMultiColumnFlowThread_h