Allows setting aria labels and descriptions on elements in a
convinient way. I did not use the the .mixin. convention here for
because there's already another mixin in that folder that's also
not having .mixin. as part of its name. And then there's also no
no need to open up that extra namespace here.
If we move this upstream at some point this can be changed though.
Bug: T291284
Change-Id: I1b3d40400d539f851f13719e16ced200968a7f92
