reftests: Fix the background-origin test

This was broken when I accidentally removed
one of the buttons.

testsuite/reftests/background-origin.ui

@@ -6,6 +6,10 @@
       <object class="GtkBox" id="box1">
         <property name="orientation">vertical</property>
         <property name="spacing">5</property>
+        <property name="margin-top">5</property>
+        <property name="margin-bottom">5</property>
+        <property name="margin-start">5</property>
+        <property name="margin-end">5</property>
         <child>
           <object class="GtkButton" id="button1">
             <property name="name">button1</property>
@@ -14,6 +18,14 @@
             <property name="height_request">70</property>
           </object>
         </child>
+        <child>
+          <object class="GtkButton" id="button2">
+            <property name="name">button2</property>
+            <property name="receives_default">1</property>
+            <property name="width_request">144</property>
+            <property name="height_request">70</property>
+          </object>
+        </child>
         <child>
           <object class="GtkButton" id="button3">
             <property name="name">button3</property>

testsuite/reftests/meson.build

@@ -433,7 +433,6 @@ testdata = [
 
 # These need to be fixed but the issue hasn't been tracked down.
 xfails = [
-  'background-origin.ui',
   # see above
   #'sizegroups-evolution-identity-page.ui',
   # these depend on details of text layout