SVG/SMIL test-only fix: add 'reftest-wait' to a test that needs it. NPODB (also, test not currently run on tinderboxen)

layout/reftests/svg/smil/pause/init-pause-1.svg

@@ -7,7 +7,8 @@ http://www.w3.org/2003/01/REC-SVG11-20030114-errata#getCurrentTime_setCurrentTim
 
  -->
 <svg xmlns="http://www.w3.org/2000/svg"
-  onload="unpause()">
+     class="reftest-wait"
+     onload="unpause()">
   <script type="text/ecmascript"><![CDATA[
     // If we try to update the DOM as we go we very occasionally run into timing
     // issues that produce false positives for this test. So instead we just set