ASSERTION FAILED: type() == Percent in WebCore::Length::percent

Source/core/rendering/AutoTableLayout.cpp

 /*
  * Copyright (C) 2002 Lars Knoll (knoll@kde.org)
  *           (C) 2002 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2008, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License.
  *
@@ skipping 275 matching lines @@
     }
 
     for (size_t i = 0; i < m_spanCells.size(); ++i) {
         RenderTableCell* cell = m_spanCells[i];
         if (!cell)
             break;
 
         unsigned span = cell->colSpan();
 
         Length cellLogicalWidth = cell->styleOrColLogicalWidth();
-        if (cellLogicalWidth.isZero())
+        if (cellLogicalWidth.isZero() || cellLogicalWidth.isCalculated())

[Julien - ping for review, 2014/06/09 23:23:03]

The specification intentionally allows 'auto' in this case to avoid having to
deal with undefined table behavior. While I would prefer our implementation to
handle calc() consistently with other lengths (and the author's intent), it's a
much broader patch. I am fine with the current approach with several caveats
though:
- I filed a but about the long-term vision: https://crbug.com/382725
- we need a FIXME about having a correct implementation linking to the previous
bug.
- this change should also touch AutoTableLayout::recalcColumns() that  also
calls cell->styleOrColLogicalWidth().
- the test be converted to a check-layout.js and make sure that the auto-sizing
treats the cell / column as 'auto' if calc() is present.
- fixed table layout should have the same behavior (and thus the same testing). 

             cellLogicalWidth = Length(); // make it Auto
 
         unsigned effCol = m_table->colToEffCol(cell->col());
         size_t lastCol = effCol;
         int cellMinLogicalWidth = cell->minPreferredLogicalWidth() + spacingInRowDirection;
         int cellMaxLogicalWidth = cell->maxPreferredLogicalWidth() + spacingInRowDirection;
         float totalPercent = 0;
         int spanMinLogicalWidth = 0;
         int spanMaxLogicalWidth = 0;
         bool allColsArePercent = true;
@@ skipping 419 matching lines @@
 
     int pos = 0;
     for (size_t i = 0; i < nEffCols; ++i) {
         m_table->setColumnPosition(i, pos);
         pos += m_layoutStruct[i].computedLogicalWidth + m_table->hBorderSpacing();
     }
     m_table->setColumnPosition(m_table->columnPositions().size() - 1, pos);
 }
 
 }