Change namespace to ash for //c/b/ash/child_accounts/parent_access_code

Code in //chrome/browser/ash/child_accounts/parent_access_code is a part
of the ash-chrome, so namespace is changed to ash from chromeos.

To avoid churn during other namespace transitions in future, this CL has
temporary 'using' declarations.

This CL is part of the Chrome OS source code directory migration:
https://docs.google.com/document/d/1g-98HpzA8XcoGBWUv1gQNr4rbnD5yfvbtYZyPDDbkaE.

Change-Id: I02b3673dc807a2a6e29378274c8007b8506c48f1
Bug: 1164001
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2827564
Reviewed-by: Hidehiko Abe <[email protected]>
Owners-Override: Hidehiko Abe <[email protected]>
Commit-Queue: Yeunjoo Choi <[email protected]>
Cr-Commit-Position: refs/heads/master@{#873181}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 627eadf1..9758d92 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1113,7 +1113,7 @@
   chromeos::quick_unlock::PinStoragePrefs::RegisterProfilePrefs(registry);
   chromeos::Preferences::RegisterProfilePrefs(registry);
   chromeos::EnterprisePrintersProvider::RegisterProfilePrefs(registry);
-  chromeos::parent_access::ParentAccessService::RegisterProfilePrefs(registry);
+  ash::parent_access::ParentAccessService::RegisterProfilePrefs(registry);
   chromeos::quick_answers::prefs::RegisterProfilePrefs(registry);
   chromeos::quick_unlock::RegisterProfilePrefs(registry);
   chromeos::RegisterSamlProfilePrefs(registry);