* Rename to `sortUserSkins` to convey meaning better.
* Sort in-place instead of slicing the list.
* Change to `void` to avoid misleading users that the method returns
a new list instance.
* Fix typo in comment.
The previous code was very brittle - it was not always updating
properly, and seems to have worked either by a carefully crafted set of
circumstances, or just plain coincidence.
Having this be a get-only property avoids potential error in the future
caused by not updating the index properly, at the expense of an added
linear lookup.
Culls another non-thread-safe mutation of the `Playing` bindable.
It seems to be a weird vestige from an earlier revision of the old
"direct" panel, which relied on `DisposeOnDeathRemoval` to finish track
playback (and then was removed in
6c150c9ed7). The play button is no longer
responsible for managing preview track lifetime anyway;
`PreviewTrackManager`'s method are intended for that.
Revealed by the framework-side transform thread safety checks. `Stopped`
is even annotated as not being thread-safe (but was annotated as such
long after the class's nascence).