border-spacing is doubled between table-row-groups.

Source/core/rendering/RenderTableSection.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 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 502 matching lines @@
 #endif
 
     ASSERT(!needsLayout());
 
     RenderTableCell* cell;
 
     RenderView* viewRenderer = view();
     LayoutStateMaintainer statePusher(viewRenderer);
 
     m_rowPos.resize(m_grid.size() + 1);
-    m_rowPos[0] = table()->vBorderSpacing();
+
+    // We ignore the border-spacing on any non-top section as it is already included in the previous section's last row position.
+    if (this == table()->topSection())
+        m_rowPos[0] = table()->vBorderSpacing();
+    else
+        m_rowPos[0] = 0;
 
     SpanningRenderTableCells rowSpanCells;
 
     for (unsigned r = 0; r < m_grid.size(); r++) {
         m_grid[r].baseline = 0;
         LayoutUnit baselineDescent = 0;
 
         // Our base size is the biggest logical height from our cells' styles (excluding row spanning cells).
         m_rowPos[r + 1] = max(m_rowPos[r] + minimumValueForLength(m_grid[r].logicalHeight, 0, viewRenderer).round(), 0);
 
@@ skipping 1158 matching lines @@
     if (!style()->isLeftToRightDirection())
         cellLocation.setX(table()->columnPositions()[table()->numEffCols()] - table()->columnPositions()[table()->colToEffCol(cell->col() + cell->colSpan())] + horizontalBorderSpacing);
     else
         cellLocation.setX(table()->columnPositions()[effectiveColumn] + horizontalBorderSpacing);
 
     cell->setLogicalLocation(cellLocation);
     view()->addLayoutDelta(oldCellLocation - cell->location());
 }
 
 } // namespace WebCore