The first table row is pushed down by border-spacing.

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 810 matching lines @@
           std::max(baseline_descent,
                    cell->LogicalHeightForRowSizing() - baseline_position);
       cell_start_row_baseline_descent = baseline_descent;
     }
     row_pos_[row + 1] =
         std::max<int>(row_pos_[row + 1], row_pos_[row] + grid_[row].baseline +
                                              cell_start_row_baseline_descent);
   }
 }
 
+int LayoutTableSection::VBorderSpacingBeforeFirstRow() const {
+  // 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())
+    return 0;
+  return Table()->VBorderSpacing();
+}
+
 int LayoutTableSection::CalcRowLogicalHeight() {
 #if DCHECK_IS_ON()
   SetLayoutNeededForbiddenScope layout_forbidden_scope(*this);
 #endif
 
   DCHECK(!NeedsLayout());
 
   LayoutTableCell* cell;
 
   // We may have to forcefully lay out cells here, in which case we need a
   // layout state.
   LayoutState state(*this);
 
   row_pos_.resize(grid_.size() + 1);
-
-  // 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())
-    row_pos_[0] = Table()->VBorderSpacing();
-  else
-    row_pos_[0] = 0;
+  row_pos_[0] = VBorderSpacingBeforeFirstRow();
 
   SpanningLayoutTableCells row_span_cells;
 
   // At fragmentainer breaks we need to prevent rowspanned cells (and whatever
   // else) from distributing their extra height requirements over the rows that
   // it spans. Otherwise we'd need to refragment afterwards.
   unsigned index_of_first_stretchable_row = 0;
 
   for (unsigned r = 0; r < grid_.size(); r++) {
     grid_[r].baseline = -1;
@@ skipping 93 matching lines @@
   DCHECK(!Table()->NeedsSectionRecalc());
 
   // addChild may over-grow m_grid but we don't want to throw away the memory
   // too early as addChild can be called in a loop (e.g during parsing). Doing
   // it now ensures we have a stable-enough structure.
   grid_.ShrinkToFit();
 
   LayoutState state(*this);
 
   const Vector<int>& column_pos = Table()->EffectiveColumnPositions();
-  LayoutUnit row_logical_top;
+  LayoutUnit row_logical_top(VBorderSpacingBeforeFirstRow());
 
   SubtreeLayoutScope layouter(*this);
   for (unsigned r = 0; r < grid_.size(); ++r) {
     Row& row = grid_[r].row;
     unsigned cols = row.size();
     // First, propagate our table layout's information to the cells. This will
     // mark the row as needing layout if there was a column logical width
     // change.
     for (unsigned start_column = 0; start_column < cols; ++start_column) {
       CellStruct& current = row[start_column];
@@ skipping 1190 matching lines @@
 bool LayoutTableSection::PaintedOutputOfObjectHasNoEffectRegardlessOfSize()
     const {
   // LayoutTableSection paints background from columns.
   if (Table()->HasColElements())
     return false;
   return LayoutTableBoxComponent::
       PaintedOutputOfObjectHasNoEffectRegardlessOfSize();
 }
 
 }  // namespace blink