[orca-list] Sometimes I can not scroll in a page after alt+tab to firefox

[José Vilmar Estácio de Souza <vilmar informal com br>]

Hi all.
To reproduce try the following steps.
1. Make sure that you are running latest orca from master.
2. Launch firefox and navigate to 
http://grails.github.io/grails-doc/2.4.0/guide/introduction.html, 
although I suspect that this can be seem in other pages too.

3. After the page is load use arrows to explore the content of the page.
4. Switch to other window using alt+ta and press some keys.
5. Switch back to firefox using alt+tab and try to use the arrows to 
explore the content of the page.

In my machine orca stays mute. This does not always happen but I can 
reproduce quite often.
Does not happen with orca 3.16.2.
Thanks.

--
José Vilmar Estácio de Souza