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

Source/core/rendering/AutoTableLayout.cpp

Index: Source/core/rendering/AutoTableLayout.cpp
diff --git a/Source/core/rendering/AutoTableLayout.cpp b/Source/core/rendering/AutoTableLayout.cpp
index eec5a0cd9f63a4fdf8ed79387308db06ee725ad3..86a0944c178a78c5ffef7988598f479050edf107 100644
--- a/Source/core/rendering/AutoTableLayout.cpp
+++ b/Source/core/rendering/AutoTableLayout.cpp
@@ -293,7 +293,7 @@ int AutoTableLayout::calcEffectiveLogicalWidth()
         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());