Firefox hover doesn't respect highlighted option in a select ng-options after digest

[heymatthew]

This issue was raised on the mailing list about a year ago (03/2013) and a patch was hacked together. This was cited as an issue with 1.0.6 but still appears to be an issue affecting both 1.2.x and master.

Discussion on the mailing list around this issue can be found here:
https://groups.google.com/forum/#!topic/angular/Ry6_b6XaobA

I've got a page with $timeout events firing that update a time set in $scope that is rendered in the page. When these timers fire, if you happen to have a select that's rendered with ng-options open in firefox, it will try to change the currently selected item while you're trying to interact with the dropdown menu. This is disorientating as the menu appears to thrash about.

Reproduction steps:

1. Go to this plunkr page in firefox: http://plnkr.co/edit/rSohihJdsZ4zQ4hMnsKH?p=preview
2. Make sure it's running, and that Live Preview is open (LHS, the eye icon)
3. Click the dropdown dialog, hover over another colour, and wait 1 second.

What happens?
After 1 second, the tries to set the current highlighted option back to what it is in the model. What should happen? The select shouldn't change the currently highlighted option, nor the selection in the bound model till the user chooses one of the options from the dropdown. This appears to be a regression relating to issue #599 from commit ee6af9a which was a fix for an IE9 bug in the context of having null options. The proposed patch basically puts the code back to pre ee6af9a.

[heymatthew]

Closing this bug as a duplicate of #5994.