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

chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc

Index: chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc
diff --git a/chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc b/chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc
index 2c7f590e3c421f3c204554ff3a620bf2961b3547..a4278ed5f0b3bfc6a366befe3fc02ea885400782 100644
--- a/chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc
+++ b/chrome/browser/chromeos/policy/cloud_external_data_policy_observer.cc
@@ -38,7 +38,7 @@ class CloudExternalDataPolicyObserver::PolicyServiceObserver
     : public PolicyService::Observer {
  public:
   PolicyServiceObserver(CloudExternalDataPolicyObserver* parent,
-                        const std::string& user_id,
+                        const user_manager::UserID& user_id,
                         PolicyService* policy_service);
   ~PolicyServiceObserver() override;
 
@@ -49,7 +49,7 @@ class CloudExternalDataPolicyObserver::PolicyServiceObserver
 
  private:
   CloudExternalDataPolicyObserver* parent_;
-  const std::string user_id_;
+  const user_manager::UserID user_id_;
   PolicyService* policy_service_;
 
   DISALLOW_COPY_AND_ASSIGN(PolicyServiceObserver);
@@ -57,7 +57,7 @@ class CloudExternalDataPolicyObserver::PolicyServiceObserver
 
 CloudExternalDataPolicyObserver::PolicyServiceObserver::PolicyServiceObserver(
     CloudExternalDataPolicyObserver* parent,
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     PolicyService* policy_service)
     : parent_(parent),
       user_id_(user_id),
@@ -102,17 +102,17 @@ void CloudExternalDataPolicyObserver::PolicyServiceObserver::OnPolicyUpdated(
 
 void CloudExternalDataPolicyObserver::Delegate::OnExternalDataSet(
     const std::string& policy,
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
 }
 
 void CloudExternalDataPolicyObserver::Delegate::OnExternalDataCleared(
     const std::string& policy,
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
 }
 
 void CloudExternalDataPolicyObserver::Delegate::OnExternalDataFetched(
     const std::string& policy,
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     scoped_ptr<std::string> data) {
 }
 
@@ -175,7 +175,7 @@ void CloudExternalDataPolicyObserver::Observe(
     return;
   }
 
-  const std::string& user_id = user->email();
+  const user_manager::UserID& user_id = user->GetUserID();
   if (ContainsKey(logged_in_user_observers_, user_id)) {
     NOTREACHED();
     return;
@@ -190,7 +190,7 @@ void CloudExternalDataPolicyObserver::Observe(
 }
 
 void CloudExternalDataPolicyObserver::OnPolicyUpdated(
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
   if (ContainsKey(logged_in_user_observers_, user_id)) {
     // When a device-local account is logged in, a policy change triggers both
     // OnPolicyUpdated() and PolicyServiceObserver::OnPolicyUpdated(). Ignore
@@ -252,7 +252,7 @@ void CloudExternalDataPolicyObserver::RetrieveDeviceLocalAccounts() {
 
   std::vector<DeviceLocalAccount> device_local_account_list =
       policy::GetDeviceLocalAccounts(cros_settings_);
-  std::set<std::string> device_local_accounts;
+  std::set<user_manager::UserID> device_local_accounts;
   for (std::vector<DeviceLocalAccount>::const_iterator it =
            device_local_account_list.begin();
        it != device_local_account_list.end(); ++it) {
@@ -263,7 +263,7 @@ void CloudExternalDataPolicyObserver::RetrieveDeviceLocalAccounts() {
            device_local_account_entries_.begin();
        it != device_local_account_entries_.end(); ) {
     if (!ContainsKey(device_local_accounts, it->first)) {
-      const std::string user_id = it->first;
+      const user_manager::UserID user_id = it->first;
       it->second.DeleteOwnedMembers();
       device_local_account_entries_.erase(it++);
       // When a device-local account whose external data reference was set is
@@ -275,14 +275,14 @@ void CloudExternalDataPolicyObserver::RetrieveDeviceLocalAccounts() {
     }
   }
 
-  for (std::set<std::string>::const_iterator it = device_local_accounts.begin();
+  for (std::set<user_manager::UserID>::const_iterator it = device_local_accounts.begin();
        it != device_local_accounts.end(); ++it) {
     OnPolicyUpdated(*it);
   }
 }
 
 void CloudExternalDataPolicyObserver::HandleExternalDataPolicyUpdate(
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     const PolicyMap::Entry* entry) {
   if (!entry) {
     delegate_->OnExternalDataCleared(policy_, user_id);
@@ -305,7 +305,7 @@ void CloudExternalDataPolicyObserver::HandleExternalDataPolicyUpdate(
 }
 
 void CloudExternalDataPolicyObserver::OnExternalDataFetched(
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     scoped_ptr<std::string> data) {
   FetchWeakPtrMap::iterator it = fetch_weak_ptrs_.find(user_id);
   DCHECK(it != fetch_weak_ptrs_.end());