[orca-list] Problem with Firefox

[Arkadiusz Kozioł <zywek-mailing nvps pl>]

I'm using the newest master commit on github, and I have problem. When 
I'm trying to navigate on pages by headers, Cursor does not move to 
heading.

Steps to reproduce:

1. Open Youtube subscriptions in firefox

2. Press h until you hear some movie which appear

3. Press tab

Orca will be on a top of the page.