Get rid of a lot of special code for RenderFlowThread invalidation.

Source/core/rendering/RenderMultiColumnSet.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 95 matching lines @@
     // Reset previously calculated column height. Will mark for layout if needed.
     void resetColumnHeight();
 
     // Expand this set's flow thread portion rectangle to contain all trailing flow thread
     // overflow. Only to be called on the last set.
     void expandToEncompassFlowThreadContentsIfNeeded();
 
     void attachRegion();
     void detachRegion();
 
-    void paintInvalidationForFlowThreadContent(const LayoutRect& paintInvalidationRect);
-
     // The top of the nearest page inside the region. For RenderRegions, this is just the logical top of the
     // flow thread portion we contain. For sets, we have to figure out the top of the nearest column or
     // page.
     LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const;
 
     void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect);
 
     LayoutUnit columnGap() const;
 
     // The "CSS actual" value of column-count. This includes overflowing columns, if any.
@@ skipping 74 matching lines @@
     };
     Vector<ContentRun, 1> m_contentRuns;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet());
 
 } // namespace blink
 
 #endif // RenderMultiColumnSet_h