nt elements and their
        // corresponding distributed nodes to implement a contains-like method
        // that pierces through the composed tree of the ShadowDOM. Results of
        // this operation are cached (elsewhere) on a per-scroll-lock basis, to
        // guard against potentially expensive lookups happening repeatedly as
        // a user scrolls / touchmoves.
        var contentElements;
        var distributedNodes;
        var contentIndex;
        var nodeIndex;

        if (element.cont