[DO NOT COMMIT] Don't keep pointers to table sections when told to recalculate sections.

third_party/WebKit/Source/core/layout/LayoutTableSection.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2013 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
@@ skipping 2045 matching lines @@
       return false;
   }
 
   return true;
 }
 
 bool LayoutTableSection::mapToVisualRectInAncestorSpace(
     const LayoutBoxModelObject* ancestor,
     LayoutRect& rect,
     VisualRectFlags flags) const {
+  DCHECK(!needsLayout());
   if (ancestor == this)
     return true;
   // Repeating table headers are painted once per fragmentation page/column.
   // This does not go through the regular fragmentation machinery, so we need
   // special code to expand the invalidation rect to contain all positions of
   // the header in all columns.
   // Note that this is in flow thread coordinates, not visual coordinates. The
   // enclosing LayoutFlowThread will convert to visual coordinates.
   if (table()->header() == this && isRepeatingHeaderGroup())
     rect.setHeight(table()->logicalHeight());
   return LayoutTableBoxComponent::mapToVisualRectInAncestorSpace(ancestor, rect,
                                                                  flags);
 }
 
 }  // namespace blink