Open help app when 'Need help' button is pressed on parent access dialog

Help app will present help topic about parent access code:
https://support.google.com/families/answer/7307262
This change requires submitting new offline resources to
chromeos-assets (WIP).

Bug: 941702
Test: ParentAccessViewTest + manually
Change-Id: Ib7d9846e1e8bc4da3ce3ebb803a5d621994699d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1764750
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Henrique Grandinetti <hgrandinetti@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689537}

diff --git a/ash/login/login_screen_controller.cc b/ash/login/login_screen_controller.cc
index d18db4b..a6b5c70f 100644
--- a/ash/login/login_screen_controller.cc
+++ b/ash/login/login_screen_controller.cc

@@ -449,6 +449,10 @@
   client_->ShowAccountAccessHelpApp();
 }
 
+void LoginScreenController::ShowParentAccessHelpApp() {
+  client_->ShowParentAccessHelpApp();
+}
+
 void LoginScreenController::ShowLockScreenNotificationSettings() {
   client_->ShowLockScreenNotificationSettings();
 }