Simplified BoxPainter edge adjacency test.

Source/core/paint/BoxPainter.cpp

Index: Source/core/paint/BoxPainter.cpp
diff --git a/Source/core/paint/BoxPainter.cpp b/Source/core/paint/BoxPainter.cpp
index efeaf5eceaeef4ae23bf487982c22b740d70a34b..848a30fa949c696ad9db8cd1f3a4f69930757655 100644
--- a/Source/core/paint/BoxPainter.cpp
+++ b/Source/core/paint/BoxPainter.cpp
@@ -1710,10 +1710,9 @@ void BoxPainter::paintBorder(LayoutBoxModelObject& obj, const PaintInfo& info, c
 
 static inline bool includesAdjacentEdges(BorderEdgeFlags flags)
 {
-    return (flags & (TopBorderEdge | RightBorderEdge)) == (TopBorderEdge | RightBorderEdge)
-        || (flags & (RightBorderEdge | BottomBorderEdge)) == (RightBorderEdge | BottomBorderEdge)
-        || (flags & (BottomBorderEdge | LeftBorderEdge)) == (BottomBorderEdge | LeftBorderEdge)
-        || (flags & (LeftBorderEdge | TopBorderEdge)) == (LeftBorderEdge | TopBorderEdge);
+    // The set includes adjacent edges iff it contains at least one horizontal and one vertical edge.
+    return (flags & (TopBorderEdge | BottomBorderEdge))
+        && (flags & (LeftBorderEdge | RightBorderEdge));
 }
 
 void BoxPainter::paintTranslucentBorderSides(GraphicsContext* graphicsContext, const ComputedStyle& style,