Disable the test on Windows, since it just can't pass there. Followup for bug 731447.

layout/reftests/text-decoration/reftest.list

@@ -98,5 +98,5 @@ fails == underline-block-propagation-2-quirks.html underline-block-propagation-2
 != inline-baseline-quirks.html inline-baseline-quirks-ref.html
 == 676538-1.html 676538-1-ref.html
 == underline-button-1.html underline-button-1-ref.html
-== underline-button-2.html underline-button-2-ref.html
+fails-if(winWidget) == underline-button-2.html underline-button-2-ref.html # On windows, the underline spacing inside the button is different