Intermittent timeout in /_mozilla/css/iframe/hide_after_load.html, /css-backgrounds-3_dev/html4/box-shadow-syntax-001.htm, /css/css-backgrounds/box-shadow-syntax-001.xht

```
 ▶ TIMEOUT [expected PASS] /_mozilla/css/iframe/hide_after_load.html
  │ 
  │ VMware, Inc.
  │ Gallium 0.4 on softpipe
  └ 3.3 (Core Profile) Mesa 12.0.1
```