better AppleScript support [M608049]

```
This is essentially bug https://bugzilla.mozilla.org/show_bug.cgi?id=608049 ; 
we could use their patch. However, Mozilla doesn't seem to interested in 
completing the API, so this may need to wait until we are no longer at source 
or widget parity.
```

Original issue reported on code.google.com by `classi...@floodgap.com` on 9 Jun 2012 at 12:24
- Blocked on: #89
