Col width is not honored when dynamically updated and it would not make table narrower

Source/core/rendering/RenderTableCol.cpp

Index: Source/core/rendering/RenderTableCol.cpp
diff --git a/Source/core/rendering/RenderTableCol.cpp b/Source/core/rendering/RenderTableCol.cpp
index 26c5935f97f1d3bd065cfbc31b1acc90e6fc6c8a..a1d973650a2ecd271bd065dbc747880a0d04705c 100644
--- a/Source/core/rendering/RenderTableCol.cpp
+++ b/Source/core/rendering/RenderTableCol.cpp
@@ -51,8 +51,24 @@ void RenderTableCol::styleDidChange(StyleDifference diff, const RenderStyle* old
     // If border was changed, notify table.
     if (parent()) {
         RenderTable* table = this->table();
-        if (table && !table->selfNeedsLayout() && !table->normalChildNeedsLayout() && oldStyle && oldStyle->border() != style()->border())
+        if (table && !table->selfNeedsLayout() && !table->normalChildNeedsLayout() && oldStyle && oldStyle->border() != style()->border()) {
             table->invalidateCollapsedBorders();
+        } else if (oldStyle && oldStyle->width() != style()->width()) {

[Julien - ping for review, 2014/02/06 22:28:18]

I don't think this is right: you need to check logical direction so it should be
logicalWidth() here, not width().

This should be covered by a vertical writing mode test case too as it was missed
in the code.

+            for (RenderObject* child = table->children()->firstChild(); child; child = child->nextSibling()) {
+                if (child->isTableSection()) {

[Julien - ping for review, 2014/02/06 22:28:18]

We prefer early return so I would expect us to prefer also early continue (to
avoid lost of nested blocks of code).

+                    RenderTableSection* section = toRenderTableSection(child);
+                    unsigned nEffCols = table->numEffCols();
+                    for (unsigned j = 0; j < nEffCols; j++) {
+                        for (unsigned i = 0; i < section->numRows(); i++) {
+                            RenderTableCell* cell = section->primaryCellAt(i, j);
+                            if (!cell)
+                                continue;
+                            cell->setPreferredLogicalWidthsDirty();
+                        }
+                    }
+                }

[Julien - ping for review, 2014/02/06 22:28:18]

You are basically dirtying the preferred logical widths for all the cells, which
is totally overblown.

Only the cells in the current column should need their preferred logical widths
recomputed.

+            }
+        }
     }
 }