diff -r 000000000000 -r 6474c204b198 dom/plugins/test/reftest/plugin-background.css
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/plugins/test/reftest/plugin-background.css	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+div {
+  position: absolute;
+}
+#bad {
+  left:220px; top:0px;
+  z-index: 0;
+}
+#good {
+  left:0px; top:0px;
+  width:220px; height:220px;
+  /* Core Animation alpha blending rounding differs
+     from the Core Graphics blending, adjust with care */
+  background-color: rgba(0,255,0, 0.51);
+  z-index: 0;
+}
+
+#topbar {
+  left:0px; top:0px;
+  width:220px; height:20px;
+  background-color: rgb(0,0,0);
+  z-index: 2;
+}
+#topbar {
+  left:0px; top:0px;
+  width:220px; height:20px;
+  background-color: rgb(0,0,0);
+  z-index: 2;
+}
+#leftbar {
+  left:0px; top:0px;
+  width:20px; height:220px;
+  background-color: rgb(0,0,0);
+  z-index: 2;
+}
+#rightbar {
+  left:200px; top:0px;
+  width:20px; height:220px;
+  background-color: rgb(0,0,0);
+  z-index: 2;
+}
+#bottombar {
+  left:0px; top:200px;
+  width:220px; height:20px;
+  background-color: rgb(0,0,0);
+  z-index: 2;
+}
+
+div#plugin {
+  position: absolute;
+  left:1px; top:1px;
+  width:199px; height:199px;
+  background-color: rgba(0,0,255, 0.2);
+  z-index: 1;
+}
+
+embed#plugin {
+  position: absolute;
+  left:1px; top:1px;
+  z-index: 1;
+}
+