Top-align table cells in rows that cross fragmentainer boundaries.

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 1157 matching lines @@
       if (!cell || cs.inColSpan)
         continue;
 
       int rowIndex = cell->rowIndex();
       int rHeight =
           m_rowPos[rowIndex + cell->rowSpan()] - m_rowPos[rowIndex] - vspacing;
 
       relayoutCellIfFlexed(*cell, r, rHeight);
 
       SubtreeLayoutScope layouter(*cell);
-      cell->computeIntrinsicPadding(rHeight, layouter);
+      LayoutUnit rowLogicalTop(m_rowPos[rowIndex]);
+      EVerticalAlign cellVerticalAlign;
+      // If the cell crosses a fragmentainer boundary, just align it at the
+      // top. That's how it was laid out initially, before we knew the final
+      // row height, and re-aligning it now could result in the cell being
+      // fragmented differently, which could change its height and thus violate
+      // the requested alignment. Give up instead of risking circular
+      // dependencies and unstable layout.
+      if (crossesPageBoundary(rowLogicalTop, LayoutUnit(rHeight)))
+        cellVerticalAlign = VerticalAlignTop;
+      else
+        cellVerticalAlign = cell->style()->verticalAlign();
+      cell->computeIntrinsicPadding(rHeight, cellVerticalAlign, layouter);
 
       LayoutRect oldCellRect = cell->frameRect();
 
       setLogicalPositionForCell(cell, c);
 
       if (!cell->needsLayout())
         markChildForPaginationRelayoutIfNeeded(*cell, layouter);
 
       cell->layoutIfNeeded();
 
@@ skipping 809 matching lines @@
   // 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