Files app: Add id to new breadcrumbs

This makes the tabindex integration tests failure message more obvious.
The test is based on the id of elements receiving focus.

Bug: 1035691, 992818
Change-Id: I72ebbeb35927cbfa07c246b6bdf4d0b20f4bc427
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2088971
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747121}

ui/file_manager/file_manager/foreground/js/ui/location_line.js

@@ -196,6 +196,7 @@ class LocationLine extends cr.EventTarget {
     let breadcrumbs = document.querySelector('bread-crumb');
     if (!breadcrumbs) {
       breadcrumbs = document.createElement('bread-crumb');
+      breadcrumbs.id = 'breadcrumbs';
       this.breadcrumbs_.appendChild(breadcrumbs);
       breadcrumbs.setSignalCallback(this.breadCrumbSignal_.bind(this));
     }