diff --git a/gfx/2d/Types.h b/gfx/2d/Types.h
index ebd72f2391..4a3b26c811 100644
--- a/gfx/2d/Types.h
+++ b/gfx/2d/Types.h
@@ -464,6 +464,11 @@ constexpr bool HalfCornerIsX(HalfCorner aHalfCorner)
   return !(aHalfCorner % 2);
 }
 
+constexpr Corner HalfToFullCorner(HalfCorner aHalfCorner)
+{
+  return Corner(aHalfCorner / 2);
+}
+
 } // namespace mozilla
 
 #endif /* MOZILLA_GFX_TYPES_H_ */
diff --git a/layout/style/nsStyleConsts.h b/layout/style/nsStyleConsts.h
index 8ed98de230..e076025f4e 100644
--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@@ -20,7 +20,6 @@ namespace mozilla {
 // nsStyleCoord.cpp.
 // Arguments must not have side effects.
 
-#define NS_HALF_TO_FULL_CORNER(var_) ((var_)/2)
 #define NS_FULL_TO_HALF_CORNER(var_, vert_) ((var_)*2 + !!(vert_))
 
 #define NS_SIDE_IS_VERTICAL(side_) ((side_) % 2)
diff --git a/layout/style/nsStyleCoord.cpp b/layout/style/nsStyleCoord.cpp
index 1c1b100d1b..a7b5413357 100644
--- a/layout/style/nsStyleCoord.cpp
+++ b/layout/style/nsStyleCoord.cpp
@@ -352,10 +352,10 @@ CASE(eCornerBottomLeftX,  true);
 CASE(eCornerBottomLeftY,  false);
 #undef CASE
 
-// Validation of NS_HALF_TO_FULL_CORNER.
+// Validation of HalfToFullCorner.
 #define CASE(corner, result)                                                  \
-  static_assert(NS_HALF_TO_FULL_CORNER(corner) == result,                     \
-                "NS_HALF_TO_FULL_CORNER is wrong")
+  static_assert(HalfToFullCorner(corner) == result,                     \
+                "HalfToFullCorner is wrong")
 CASE(eCornerTopLeftX,     eCornerTopLeft);
 CASE(eCornerTopLeftY,     eCornerTopLeft);
 CASE(eCornerTopRightX,    eCornerTopRight);