Outline in selected element in friends menu cannot be retextured

Relates to: MC-268805 MC-268927 MC-269079 MC-269364 MC-269365 MC-269437 MC-269438 MC-269443 MC-269447 MC-269938 MC-269939 MC-270254 MC-270255 MC-270256 MC-270257 MC-270258 MC-270260 MC-270324 MC-270766 MC-273060 MC-275778 MC-276442 MC-276635 MC-276664 MC-277504 MC-277696 MC-277705 MC-277706 MC-277877 MC-278170 MC-278171 MC-278412 MC-278413 MC-278414 MC-278415 MC-278507 MC-300295

Snapshot 7 adds the ability to navigate friends via the keyboard. With it came a new visual rectangle that appears around whatever account you’re looking at. Unlike almost all other graphics in this screen, this is an entirely hardcoded graphic which does not depend on a nine-slice texture file, and therefore resource packs are entirely incapable of configuring it.

To fix, this should be a texture file, not code-generated, for consistency.