Move hidden style to HTML

layout/reftests/first-line/stress-10.html

@@ -1,6 +1,6 @@
 <style>
 *::first-line { }
 *::before { content:"before text";}
-body { visibility: hidden }
+html { visibility: hidden }
 </style>
 <object style="position: fixed;-moz-column-count: 100;"><ol style="float: right;">