--- a/layout/base/Units.h
+++ b/layout/base/Units.h
@@ -666,11 +666,37 @@ gfx::ScaleFactor<src, dst> MaxScaleRatio
 }
 
 template<class src, class dst>
 gfx::ScaleFactor<src, dst> MinScaleRatio(const gfx::SizeTyped<dst>& aDestSize, const gfx::SizeTyped<src>& aSrcSize) {
   return gfx::ScaleFactor<src, dst>(std::min(aDestSize.width / aSrcSize.width,
                                              aDestSize.height / aSrcSize.height));
 }
 
+template <typename T>
+struct CoordOfImpl;
+
+template <typename Units>
+struct CoordOfImpl<gfx::PointTyped<Units>> {
+  typedef gfx::CoordTyped<Units> Type;
+};
+
+template <typename Units>
+struct CoordOfImpl<gfx::IntPointTyped<Units>> {
+  typedef gfx::IntCoordTyped<Units> Type;
+};
+
+template <typename Units>
+struct CoordOfImpl<gfx::RectTyped<Units>> {
+  typedef gfx::CoordTyped<Units> Type;
+};
+
+template <typename Units>
+struct CoordOfImpl<gfx::IntRectTyped<Units>> {
+  typedef gfx::IntCoordTyped<Units> Type;
+};
+
+template <typename T>
+using CoordOf = typename CoordOfImpl<T>::Type;
+
 } // namespace mozilla
 
 #endif