Add reftest to reftest.list

layout/reftests/bugs/reftest.list

@@ -882,3 +882,4 @@ fails == 441259-2.html 441259-2-ref.html # bug 441400
 == 449519-1.html 449519-1-ref.html
 # == 449653-1.html 449653-1-ref.html # Disabled for now - it needs privileges
 == 450670-1.html 450670-1-ref.html
+== 451168-1.html 451168-1-ref.html