Negative row height when cell has percentage height.

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)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 295 matching lines @@
     // Our algorithm matches Firefox. Extra spanning height would be distributed Only in first percent height rows
     // those total percent is 100. Other percent rows would be uneffected even extra spanning height is remain.
     int accumulatedPositionIncrease = 0;
     for (unsigned row = rowIndex; row < (rowIndex + rowSpan); row++) {
         if (percent > 0 && extraRowSpanningHeight > 0) {
             if (m_grid[row].logicalHeight.isPercent()) {
                 int toAdd = (tableHeight * m_grid[row].logicalHeight.percent() / 100) - rowsHeight[row - rowIndex];
                 // FIXME: Note that this is wrong if we have a percentage above 100% and may make us grow
                 // above the available space.
 
+                toAdd = std::max(toAdd, 0);

[esprehn, 2015/03/26 08:23:11]

How does toAdd become negative here?

[a.suchit2, 2015/03/26 09:38:35]

If percent height is less than the rowHeight based on the content in the cells
of the row then percent height should be ignored.

just consider : 
rowsHeight[row - rowIndex] -> 10 px => this is the row height based on content
on the cells of this row.

Total table height is 20 px

then 1% (percent height for the row) of 20 px is 2.

toAdd become 2 - 20 = -18

[Julien - ping for review, 2015/03/26 15:22:10]

It's not the only place where we do something similar and it's reasonable to do
so here IMO.

                 toAdd = std::min(toAdd, extraRowSpanningHeight);
                 accumulatedPositionIncrease += toAdd;
                 extraRowSpanningHeight -= toAdd;
                 percent -= m_grid[row].logicalHeight.percent();
             }
         }
         m_rowPos[row + 1] += accumulatedPositionIncrease;
     }
 }
 
@@ skipping 1278 matching lines @@
     // FIXME: The table's direction should determine our row's direction, not the section's (see bug 96691).
     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);
 }
 
 } // namespace blink