after-set-position in mode:host-text-mixin

Called after the start and end position have been moved (but not when the position is moved due to inserts or deletes).

See also on-edit-sequence.

• (send a-mode:host-text-mixin after-set-position orig super-call) -> ???
     orig : ???
     super-call : (??? -> ???)

  If a surrogate is set, calls the surrogate with the arguments it was passed, plus this and a function that calls the super method.

  if a surrogate is not set, calls the super method and returns that result.