diff -r 000000000000 -r 6474c204b198 layout/style/test/support/external-variable-url.css
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/style/test/support/external-variable-url.css	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,3 @@
+div {
+  --a: url('image.png');
+}