ChromeOS cryptohome should be able to use gaia id as user identifier.

chrome/browser/chromeos/app_mode/kiosk_app_data.cc

Index: chrome/browser/chromeos/app_mode/kiosk_app_data.cc
diff --git a/chrome/browser/chromeos/app_mode/kiosk_app_data.cc b/chrome/browser/chromeos/app_mode/kiosk_app_data.cc
index ed463867e4bfab71e4b3cdfeaebe7d21f6fac437..0cb0c989ac6267c6d54ff3f2e6b167465addcf2d 100644
--- a/chrome/browser/chromeos/app_mode/kiosk_app_data.cc
+++ b/chrome/browser/chromeos/app_mode/kiosk_app_data.cc
@@ -395,14 +395,13 @@ class KioskAppData::WebstoreDataParser
 
 KioskAppData::KioskAppData(KioskAppDataDelegate* delegate,
                            const std::string& app_id,
-                           const std::string& user_id,
+                           const AccountId& account_id,
                            const GURL& update_url)
     : delegate_(delegate),
       status_(STATUS_INIT),
       app_id_(app_id),
-      user_id_(user_id),
-      update_url_(update_url) {
-}
+      account_id_(account_id),
+      update_url_(update_url) {}
 
 KioskAppData::~KioskAppData() {}