Dropdown's arrow key handler runs global DOM query?

Created by: cvrebert

It seems rather odd that we're selecting all the dropdown items in the entire document in https://github.com/twbs/bootstrap/blob/2f176821c3c5439f83a5df4a176534d724e716b9/js/src/dropdown.js#L233 Surely we should be limiting the query to the descendants of the relevant dropdown menu? It seems rather unnecessarily wasteful otherwise.