New avatar button: Update when the supervised user ID changes.

chrome/browser/profiles/profile_info_cache.cc

Index: chrome/browser/profiles/profile_info_cache.cc
diff --git a/chrome/browser/profiles/profile_info_cache.cc b/chrome/browser/profiles/profile_info_cache.cc
index 18919a8d85651a5b36d2c97733e59f877f51f95d..a6f8d9abb02caa453cd2642ea2aa49105abb51bc 100644
--- a/chrome/browser/profiles/profile_info_cache.cc
+++ b/chrome/browser/profiles/profile_info_cache.cc
@@ -554,6 +554,11 @@ void ProfileInfoCache::SetSupervisedUserIdOfProfileAtIndex(
   info->SetString(kSupervisedUserId, id);
   // This takes ownership of |info|.
   SetInfoForProfileAtIndex(index, info.release());
+
+  base::FilePath profile_path = GetPathOfProfileAtIndex(index);
+  FOR_EACH_OBSERVER(ProfileInfoCacheObserver,
+                    observer_list_,
+                    OnProfileSupervisedUserIdChanged(profile_path));
 }
 
 void ProfileInfoCache::SetLocalAuthCredentialsOfProfileAtIndex(