Demo Mode: Add cros-essential-apps-dev+watch@ to watch demo mode files.

Change-Id: I4ccc6d5df5ec248d20e35b04d91fe3be762f68e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094420
Commit-Queue: Leo Zhang <googleo@chromium.org>
Reviewed-by: Leo Zhang <googleo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748498}

WATCHLISTS

@@ -919,6 +919,11 @@
     'dbus': {
       'filepath': 'dbus/',
     },
+    'demo_mode': {
+      'filepath': 'docs/login/demo_mode.md|'\
+                  'chrome/browser/chromeos/login/demo_mode/|'\
+                  'ash/metrics/demo_session_metrics_recorder.*',
+    },
     'device_bluetooth': {
       'filepath': 'device/.*bluetooth'
     },
@@ -2414,6 +2419,7 @@
                     'pshmakov+watch@chromium.org'],
     'data_decoder': ['mbarowsky+watch-data-decoder@chromium.org'],
     'dbus': ['hashimoto+watch@chromium.org'],
+    'demo_mode': ['cros-essential-apps-dev+watch@chromium.org'],
     'device_bluetooth': ['mattreynolds+watch@chromium.org',
                          'ortuno+watch@chromium.org'],
     'device_chooser': ['juncai+watch@chromium.org',