--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@@ -141,16 +141,27 @@ enum class StyleClipPathGeometryBox : ui
   Padding,
   Border,
   Margin,
   Fill,
   Stroke,
   View,
 };
 
+// background-origin/ mask-origin.
+enum class StyleImageLayerOrigin : uint8_t {
+  Content,
+  Padding,
+  Border,
+  Margin,  // mask-origin only.
+  Fill,    // mask-origin only.
+  Stroke,  // mask-origin only.
+  View     // mask-origin only.
+};
+
 // fill-rule
 enum class StyleFillRule : uint8_t {
   Nonzero,
   Evenodd,
 };
 
 // float
 // https://developer.mozilla.org/en-US/docs/Web/CSS/float