Bug 572899 - Reftest mathml/semantics-1.xhtml fails with STIX 1.0.0. r=karlt

layout/reftests/mathml/semantics-1-ref.xhtml

@@ -23,7 +23,7 @@
 <!-- embellished operator (bug 21479) -->
 <p><math xmlns="http://www.w3.org/1998/Math/MathML">
   <mover>
-    <mtext>■□■□■□■□■□■□</mtext>
+    <mspace width="300px" height="10px" mathbackground="black"></mspace>
     <mo>&#xaf;</mo>
   </mover>
 </math></p>

layout/reftests/mathml/semantics-1.xhtml

@@ -21,7 +21,7 @@
 <!-- embellished operator (bug 21479) -->
 <p><math xmlns="http://www.w3.org/1998/Math/MathML">
   <mover>
-    <mtext>■□■□■□■□■□■□</mtext>
+    <mspace width="300px" height="10px" mathbackground="black"></mspace>
     <semantics><mo>&#xaf;</mo></semantics>
   </mover>
 </math></p>