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

third_party/WebKit/Source/core/style/BorderData.h

Index: third_party/WebKit/Source/core/style/BorderData.h
diff --git a/third_party/WebKit/Source/core/style/BorderData.h b/third_party/WebKit/Source/core/style/BorderData.h
index 72d28e16e2dfdf9493becd948cda1bba14633956..4aa16c310fb1938b95b82a247ad757d56021029f 100644
--- a/third_party/WebKit/Source/core/style/BorderData.h
+++ b/third_party/WebKit/Source/core/style/BorderData.h
@@ -114,6 +114,12 @@ public:
             && m_bottomRight == o.m_bottomRight;
     }
 
+    bool visualOverflowEqual(const BorderData& o) const
+    {
+        return m_image.outset() == o.m_image.outset();
+    }
+
+

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

Nit: Extra blank line.

     bool operator!=(const BorderData& o) const
     {
         return !(*this == o);