families: Add aria label to supervision management transition dialog

This dialog is observed after a user signs in for the first time after
gellerizing their account.

Tested: Observed the vocalization of supervision dialog header

Bug: b:325662444
Change-Id: I5839196c2efe3a817a21b62be5539ce29a5c3211
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5747358
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Courtney Wong <courtneywong@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1335035}
diff --git a/chrome/browser/resources/chromeos/login/screens/login/management_transition.html b/chrome/browser/resources/chromeos/login/screens/login/management_transition.html
index 1d184e0..fd99a6df 100644
--- a/chrome/browser/resources/chromeos/login/screens/login/management_transition.html
+++ b/chrome/browser/resources/chromeos/login/screens/login/management_transition.html
@@ -22,14 +22,15 @@
 </style>
 <oobe-adaptive-dialog id="managementTransitionDialog" role="dialog"
     aria-label$="[[getDialogTitle(locale, arcTransition, managementEntity)]]"
-    for-step="progress">
+    for-step="progress" aria-live="polite"
+    aria-labelledby="managementTransitionTitle">
   <iron-icon slot="icon" icon="oobe-32:enterprise" aria-hidden="true"
     hidden="[[isChildTransition(arcTransition)]]">
   </iron-icon>
   <iron-icon slot="icon" src="images/supervision_icon.png"
     aria-hidden="true" hidden="[[!isChildTransition(arcTransition)]]">
   </iron-icon>
-  <h1 slot="title">
+  <h1 slot="title" id="managementTransitionTitle">
     [[getDialogTitle(locale, arcTransition, managementEntity)]]
   </h1>
   <div slot="subtitle">