Don't allow position:sticky for table columns.

Source/core/css/resolver/StyleAdjuster.cpp

Index: Source/core/css/resolver/StyleAdjuster.cpp
diff --git a/Source/core/css/resolver/StyleAdjuster.cpp b/Source/core/css/resolver/StyleAdjuster.cpp
index 215d499af052796dcfadab339bcc6cb48c84e9c4..fed46885afb12d66d9d3f20b1a2a8063dca05832 100644
--- a/Source/core/css/resolver/StyleAdjuster.cpp
+++ b/Source/core/css/resolver/StyleAdjuster.cpp
@@ -260,14 +260,20 @@ void StyleAdjuster::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
         if (style->display() == INLINE && style->styleType() == NOPSEUDO && style->writingMode() != parentStyle->writingMode())
             style->setDisplay(INLINE_BLOCK);
 
-        // After performing the display mutation, check table rows. We do not honor position:relative or position:sticky on
-        // table rows or cells. This has been established for position:relative in CSS2.1 (and caused a crash in containingBlock()
+        // After performing the display mutation, check table rows. We do not honor position:relativetable rows or cells.

[Julien - ping for review, 2014/03/13 01:08:06]

Nit: Space after the colon.

[ostap, 2014/03/13 15:46:45]

Done.

+        // This has been established for position:relative in CSS2.1 (and caused a crash in containingBlock()
         // on some sites).
         if ((style->display() == TABLE_HEADER_GROUP || style->display() == TABLE_ROW_GROUP
             || style->display() == TABLE_FOOTER_GROUP || style->display() == TABLE_ROW)
             && style->position() == RelativePosition)
             style->setPosition(StaticPosition);
 
+        // Do not allow position:sticky for table columns and column groups because table columns

[Julien - ping for review, 2014/03/13 01:08:06]

Same nit.

[ostap, 2014/03/13 15:46:45]

Done.

+        // don't have RenderLayer

[Julien - ping for review, 2014/03/13 01:08:06]

I don't think this is a good explanation. A better one is that we can't support
position: sticky with our current code as we only do background painting through
columns / column groups. The fact that we don't want a RenderLayer is a
consequence of that, not a cause.

[ostap, 2014/03/13 15:46:45]

Done.

+        if ((style->display() == TABLE_COLUMN_GROUP || style->display() == TABLE_COLUMN)
+            && style->position() == StickyPosition)
+            style->setPosition(StaticPosition);
+
         // writing-mode does not apply to table row groups, table column groups, table rows, and table columns.
         // FIXME: Table cells should be allowed to be perpendicular or flipped with respect to the table, though.
         if (style->display() == TABLE_COLUMN || style->display() == TABLE_COLUMN_GROUP || style->display() == TABLE_FOOTER_GROUP