Bug 1397619: Test paint-order specified value serialization. r=me

MozReview-Commit-ID: ICtzbZVix1u
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>

layout/style/test/test_specified_value_serialization.html

@@ -270,6 +270,10 @@
     }
   });
 
+  p.style.paintOrder = "markers";
+  is(p.style.paintOrder, "markers",
+     "specified value serialization for paint-order doesn't contain repetitive values");
+
   p.remove();
 })();