Simplified BoxPainter edge adjacency test.

Source/core/paint/BoxPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/BoxPainter.h"
 
 #include "core/HTMLNames.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLFrameOwnerElement.h"
@@ skipping 1692 matching lines @@
         paintTranslucentBorderSides(graphicsContext, style, outerBorder, innerBorder, borderInfo.edges,
         borderInfo.visibleEdgeSet, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias);
     } else {
         paintBorderSides(graphicsContext, style, outerBorder, innerBorder, borderInfo.edges,
         borderInfo.visibleEdgeSet, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias);
     }
 }
 
 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,
     const FloatRoundedRect& outerBorder, const FloatRoundedRect& innerBorder, const BorderEdge edges[],
     BorderEdgeFlags edgesToDraw, BackgroundBleedAvoidance bleedAvoidance, bool includeLogicalLeftEdge,
     bool includeLogicalRightEdge, bool antialias)
 {
     // willBeOverdrawn assumes that we draw in order: top, bottom, left, right.
     // This is different from BoxSide enum order.
     static const BoxSide paintOrder[] = { BSTop, BSBottom, BSLeft, BSRight };
@@ skipping 570 matching lines @@
 
     FloatPoint secondQuad[4];
     secondQuad[0] = quad[0];
     secondQuad[1] = FloatPoint(quad[0].x() - r1 * cx, quad[0].y() - r1 * cy);
     secondQuad[2] = quad[2];
     secondQuad[3] = quad[3];
     graphicsContext->clipPolygon(4, secondQuad, !secondEdgeMatches);
 }
 
 } // namespace blink