Update team drives grand root visibility when it changes.

When an onDirectoryChanged event is received for that grand root, rescan
the grand root and update its visiblity in the UI.

Bug: 854153
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ie36dabdd9348e7c174a22438b29ce8953c81d68e
Reviewed-on: https://chromium-review.googlesource.com/1136332
Reviewed-by: Sasha Morrissey <sashab@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575943}
2 files changed