Intermittent pass in /_mozilla/css/transition_calc_implicit.html

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