Move layerization_z_order_a.html to wpt reftests.

tests/ref/basic.list

@@ -161,7 +161,6 @@ prefs:"layout.writing-mode.enabled" == iframe/size_attributes_vertical_writing_m
 == jumpiness_a.html jumpiness_ref.html
 == last_child_pseudo_a.html last_child_pseudo_b.html
 == last_of_type_pseudo_a.html last_of_type_pseudo_b.html
-== layerization_z_order_a.html layerization_z_order_ref.html
 == legacy_cellspacing_attribute_a.html border_spacing_ref.html
 == legacy_input_size_attribute_override_a.html legacy_input_size_attribute_override_ref.html
 == legacy_table_border_attribute_a.html legacy_table_border_attribute_ref.html

tests/wpt/mozilla/meta/MANIFEST.json

@@ -683,6 +683,18 @@
             "url": "/_mozilla/css/flex_nochild.html"
           }
         ],
+        "css/layerization_z_order_a.html": [
+          {
+            "path": "css/layerization_z_order_a.html",
+            "references": [
+              [
+                "/_mozilla/css/layerization_z_order_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/layerization_z_order_a.html"
+          }
+        ],
         "css/nth_child_pseudo_a.html": [
           {
             "path": "css/nth_child_pseudo_a.html",
@@ -3600,6 +3612,18 @@
           "url": "/_mozilla/css/flex_nochild.html"
         }
       ],
+      "css/layerization_z_order_a.html": [
+        {
+          "path": "css/layerization_z_order_a.html",
+          "references": [
+            [
+              "/_mozilla/css/layerization_z_order_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/layerization_z_order_a.html"
+        }
+      ],
       "css/nth_child_pseudo_a.html": [
         {
           "path": "css/nth_child_pseudo_a.html",

tests/wpt/mozilla/tests/css/layerization_z_order_a.html

@@ -1,3 +1,4 @@
+<link rel='match' href='layerization_z_order_ref.html'>
 <style>
 body, html {
     margin: 0;