Add a11y alert when incorrect parent access code is entered

Change-Id: Ia92d28d7287bd14c5da2d706b266556b4b3c0de1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1793768Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695183}

ash/login/ui/parent_access_view.cc

@@ -842,6 +842,7 @@ void ParentAccessView::UpdateState(State state) {
       title_label_->SetEnabledColor(kErrorColor);
       title_label_->SetText(
           l10n_util::GetStringUTF16(IDS_ASH_LOGIN_PARENT_ACCESS_TITLE_ERROR));
+      title_label_->NotifyAccessibilityEvent(ax::mojom::Event::kAlert, true);
       return;
     }
   }