Adding or changing any of box-shadow, outline, or border-image-outset does not need a layout..

third_party/WebKit/Source/core/layout/LayoutTableRow.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. 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 219 matching lines @@
 }
 
 LayoutTableRow* LayoutTableRow::createAnonymousWithParent(const LayoutObject* parent)
 {
     LayoutTableRow* newRow = LayoutTableRow::createAnonymous(&parent->document());
     RefPtr<ComputedStyle> newStyle = ComputedStyle::createAnonymousStyleWithDisplay(parent->styleRef(), TABLE_ROW);
     newRow->setStyle(newStyle.release());
     return newRow;
 }
 
+void LayoutTableRow::recomputeOverflow()
+{
+    clearAllOverflows();
+    addVisualEffectOverflow();
+    for (LayoutTableCell* cell = firstCell(); cell; cell = cell->nextCell())
+        addOverflowFromCell(cell);
+}
+
 void LayoutTableRow::addOverflowFromCell(const LayoutTableCell* cell)
 {
     // Non-row-spanning-cells don't create overflow (they are fully contained within this row).
+    // FIXME: This seems incorrect because cell may have visual effect overflow that should be included in this row.

[Xianzhu, 2016/03/22 17:02:05]

Nit: FIXME style has been deprecated by TODO.

https://www.chromium.org/blink/coding-style#TOC-Comments

     if (cell->rowSpan() == 1)
         return;
 
     // Cells only generates visual overflow.
     LayoutRect cellVisualOverflowRect = cell->visualOverflowRectForPropagation(styleRef());
 
     // The cell and the row share the section's coordinate system. However
     // the visual overflow should be determined in the coordinate system of
     // the row, that's why we shift it below.
     LayoutUnit cellOffsetLogicalTopDifference = cell->location().y() - location().y();
     cellVisualOverflowRect.move(LayoutUnit(), cellOffsetLogicalTopDifference);
 
     addVisualOverflow(cellVisualOverflowRect);
 }
 
 } // namespace blink