We should use UserID object to identify users instead of username.

chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h

Index: chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h
diff --git a/chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h b/chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h
index fe342d8ccbe18ee9199f39d6292c5282e82d38b5..b9e991e8c9d78637121a1c3796c341dc49048de3 100644
--- a/chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h
+++ b/chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h
@@ -22,6 +22,10 @@ namespace net {
 class URLRequestContextGetter;
 }
 
+namespace user_manager {
+class UserID;
+}
+
 namespace policy {
 
 class AffiliatedCloudPolicyInvalidator;
@@ -79,9 +83,9 @@ class BrowserPolicyConnectorChromeOS
   // for details.
   EnrollmentConfig GetPrescribedEnrollmentConfig() const;
 
-  // Works out the user affiliation by checking the given |user_name| against
+  // Works out the user affiliation by checking the given |user_id| against
   // the installation attributes.
-  UserAffiliation GetUserAffiliation(const std::string& user_name);
+  UserAffiliation GetUserAffiliation(const user_manager::UserID& user_id);
 
   DeviceCloudPolicyManagerChromeOS* GetDeviceCloudPolicyManager() {
     return device_cloud_policy_manager_;