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

Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. 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
@@ skipping 2112 matching lines @@
 }
 
 bool LayoutBox::autoWidthShouldFitContent() const
 {
     return node() && (isHTMLInputElement(*node()) || isHTMLSelectElement(*node()) || isHTMLButtonElement(*node())
         || isHTMLTextAreaElement(*node()) || (isHTMLLegendElement(*node()) && !style()->hasOutOfFlowPosition()));
 }
 
 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.
         marginStart = minimumValueForLength(marginStartLength, containerWidth);
         marginEnd = minimumValueForLength(marginEndLength, containerWidth);
         return;
     }
 
     if (containingBlock->isFlexibleBox()) {
         // We need to let flexbox handle the margin adjustment - otherwise, flexbox
@@ skipping 2617 matching lines @@
 bool LayoutBox::canRenderBorderImage() const
 {
     if (!style()->hasBorderDecoration())
         return false;
 
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 } // namespace blink