Update the AvatarMenu (and the ProfileChooserView, which listens for changes to the AvatarMenu) when a supervised user's custodian info changes.

BUG=372381

Review URL: https://codereview.chromium.org/597783003

Cr-Commit-Position: refs/heads/master@{#296954}
diff --git a/chrome/browser/supervised_user/supervised_user_service.h b/chrome/browser/supervised_user/supervised_user_service.h
index 0f3a934..55e3be2 100644
--- a/chrome/browser/supervised_user/supervised_user_service.h
+++ b/chrome/browser/supervised_user/supervised_user_service.h
@@ -262,6 +262,8 @@
 
   bool ProfileIsSupervised() const;
 
+  void OnCustodianInfoChanged();
+
 #if defined(ENABLE_EXTENSIONS)
   // Internal implementation for ExtensionManagementPolicy::Delegate methods.
   // If |error| is not NULL, it will be filled with an error message if the