Bug 1022612. Part 38: Avoid test failure due to antialiased pixel leakage. r=mattwoodrow

--HG--
extra : rebase_source : 00d95d307f79720a7b597cc8ca61b40bfaa85584

layout/reftests/forms/fieldset/positioned-container-1-ref.html

@@ -4,7 +4,7 @@
 <fieldset style="position:relative; overflow:hidden; width:500px; height:500px;">
   <legend>Legend</legend>
   <div style="height:1000px;">
-    <div style="position:absolute; left:20px; top:20px; background:yellow;">Abs-pos</div>
+    <div style="position:absolute; padding:2px; left:20px; top:20px; background:yellow;">Abs-pos</div>
   </div>
 </fieldset>
 </body>

layout/reftests/forms/fieldset/positioned-container-1.html

@@ -4,7 +4,7 @@
 <fieldset id="f" style="position:relative; overflow:hidden; width:500px; height:500px;">
   <legend>Legend</legend>
   <div style="height:1000px;">
-    <div style="position:absolute; left:20px; top:50px; background:yellow;">Abs-pos</div>
+    <div style="position:absolute; padding:2px; left:20px; top:50px; background:yellow;">Abs-pos</div>
   </div>
 </fieldset>
 <script>