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

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

 /*
  * 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, 2009, 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 104 matching lines @@
             return style()->borderEnd();
 
         return style()->borderStart();
     }
 
     const BorderValue& borderAdjoiningStartCell(const LayoutTableCell*) const;
     const BorderValue& borderAdjoiningEndCell(const LayoutTableCell*) const;
 
     bool nodeAtPoint(HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override;
 
-    void addOverflowFromCell(const LayoutTableCell*);
+    void recomputeOverflow();
 
     const char* name() const override { return "LayoutTableRow"; }
 
     // Whether a row has opaque background depends on many factors, e.g. border spacing,
     // border collapsing, missing cells, etc.
     // For simplicity, just conservatively assume all table rows are not opaque.
     bool foregroundIsKnownToBeOpaqueInRect(const LayoutRect&, unsigned) const override { return false; }
     bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect&) const override { return false; }
 
 private:
+    void addOverflowFromCell(const LayoutTableCell*);
     LayoutObjectChildList* virtualChildren() override { return children(); }
     const LayoutObjectChildList* virtualChildren() const override { return children(); }
 
     bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectTableRow || LayoutBox::isOfType(type); }
 
     void willBeRemovedFromTree() override;
 
     void addChild(LayoutObject* child, LayoutObject* beforeChild = nullptr) override;
     void layout() override;
 
@@ skipping 45 matching lines @@
 
 inline LayoutTableRow* LayoutTableSection::lastRow() const
 {
     ASSERT(children() == virtualChildren());
     return toLayoutTableRow(children()->lastChild());
 }
 
 } // namespace blink
 
 #endif // LayoutTableRow_h