Intent to change: -moz-user-focus

[Emilio Cobos Álvarez]

Hi, in bug 1868552 I changed the proprietary -moz-user-focus in a couple
ways:

* -moz-user-focus: select-{all,before,after,same,menu} are removed.
These did literally nothing and behaved like -moz-user-focus: normal.

* -moz-user-focus: none actually prevents stuff from being focusable.
This only used to work for XUL.

* The initial value of -moz-user-focus is normal rather than none.

Given this property never worked as intended on anything that wasn't
XUL, I'd be surprised if it caused breakage (I did some quick code
searches and didn't find anything interesting that would break).

In the future we might want to un-expose this property from content.

Let me know if there's any concern with this.

Thanks,

-- Emilio