[DL]: Ensure that locked elements are skipped in tab order navigation

This patch ensures that the elements in a locked subtree with
searchable: false are not focusable by either mouse or keyboard. In
effect this prevents tab order navigation to elements in locked subtrees.


Bug: 882663
Change-Id: I0fbde6ba811be21021e450b38b584aa24ad7e52a
Reviewed-on: https://chromium-review.googlesource.com/c/1417715
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625287}
3 files changed