Table cells, rows, sections or column (groups) don't support margins.

Source/core/layout/LayoutBox.cpp

Index: Source/core/layout/LayoutBox.cpp
diff --git a/Source/core/layout/LayoutBox.cpp b/Source/core/layout/LayoutBox.cpp
index 36c0c273c5b5abb3310c289aa2d71bc9b8a9d42a..556dd0ef53cd93c171459cf65ed3e503901f9855 100644
--- a/Source/core/layout/LayoutBox.cpp
+++ b/Source/core/layout/LayoutBox.cpp
@@ -2130,15 +2130,12 @@ bool LayoutBox::autoWidthShouldFitContent() const
 
 void LayoutBox::computeMarginsForDirection(MarginDirection flowDirection, const LayoutBlock* containingBlock, LayoutUnit containerWidth, LayoutUnit childWidth, LayoutUnit& marginStart, LayoutUnit& marginEnd, Length marginStartLength, Length marginEndLength) const
 {
+    // First assert that we're not calling this method on box types that don't support margins.
+    ASSERT(!isTableCell());
+    ASSERT(!isTableRow());
+    ASSERT(!isTableSection());
+    ASSERT(!isLayoutTableCol());
     if (flowDirection == BlockDirection || isFloating() || isInline()) {
-        if (isTableCell() && flowDirection == BlockDirection) {
-            // FIXME: Not right if we allow cells to have different directionality than the table. If we do allow this, though,
-            // we may just do it with an extra anonymous block inside the cell.
-            marginStart = 0;
-            marginEnd = 0;
-            return;
-        }
-
         // Margins are calculated with respect to the logical width of
         // the containing block (8.3)
         // Inline blocks/tables and floats don't have their margins increased.