Extend the WATCHLIST set for notifications

This adds a number of new files and directories which should be covered
in the existing WATCHLIST entry.

R=johnme@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1045433003

Cr-Commit-Position: refs/heads/master@{#322725}

WATCHLISTS

@@ -516,6 +516,13 @@
     'notifications': {
       'filepath': 'chrome/browser/extensions/api/notifications/|' \
         'chrome/browser/notifications/|' \
+        'chrome/test/data/notifications/|' \
+        'content/browser/notifications/|' \
+        'content/child/notifications/|' \
+        'content/common/platform_notification|' \
+        'content/public/browser/platform_notification|' \
+        'content/public/common/platform_notification|' \
+        'content/renderer/notification_|' \
         'ui/message_center/'
     },
     'npapi_headers': {