Add directory to scanning watchlist

Bug: None
Change-Id: If25e328730ca156187f164e12aa57df08fad2e71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490881Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819529}

WATCHLISTS

@@ -1651,7 +1651,8 @@
                   '|components/metrics/public/mojom/call_stack*',
     },
     'scanning': {
-      'filepath': 'chromeos/components/scanning/',
+      'filepath': 'chromeos/components/scanning/'\
+                  '|chrome/browser/chromeos/scanning/',
     },
     'screen_orientation': {
       'filepath': 'screen_orientation',