Bug 1161034. Make test_animations_pausing pass even when we're doing mainthread compositing. r=birtles

layout/style/test/file_animations_pausing.html

@@ -19,6 +19,7 @@
   <script>
     var ok = opener.ok.bind(opener);
     var is = opener.is.bind(opener);
+    var todo = opener.todo.bind(opener);
     function finish() {
       var o = opener;
       self.close();