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

chrome/browser/signin/easy_unlock_screenlock_state_handler.cc

Index: chrome/browser/signin/easy_unlock_screenlock_state_handler.cc
diff --git a/chrome/browser/signin/easy_unlock_screenlock_state_handler.cc b/chrome/browser/signin/easy_unlock_screenlock_state_handler.cc
index 32f953773b325d3991f815e9f7230bd73f98f154..c3cfd8ae2f55e49edd47a6e8e0e75157155d8972 100644
--- a/chrome/browser/signin/easy_unlock_screenlock_state_handler.cc
+++ b/chrome/browser/signin/easy_unlock_screenlock_state_handler.cc
@@ -100,11 +100,11 @@ bool IsLockedState(ScreenlockState state) {
 }  // namespace
 
 EasyUnlockScreenlockStateHandler::EasyUnlockScreenlockStateHandler(
-    const std::string& user_email,
+    const user_manager::UserID& user_id,
     HardlockState initial_hardlock_state,
     proximity_auth::ScreenlockBridge* screenlock_bridge)
     : state_(ScreenlockState::INACTIVE),
-      user_email_(user_email),
+      user_id_(user_id),
       screenlock_bridge_(screenlock_bridge),
       hardlock_state_(initial_hardlock_state),
       hardlock_ui_shown_(false),
@@ -144,7 +144,7 @@ void EasyUnlockScreenlockStateHandler::ChangeState(ScreenlockState new_state) {
     return;
 
   // Do nothing when auth type is online.
-  if (screenlock_bridge_->lock_handler()->GetAuthType(user_email_) ==
+  if (screenlock_bridge_->lock_handler()->GetAuthType(user_id_) ==
       proximity_auth::ScreenlockBridge::LockHandler::ONLINE_SIGN_IN) {
     return;
   }
@@ -164,7 +164,7 @@ void EasyUnlockScreenlockStateHandler::ChangeState(ScreenlockState new_state) {
       GetIconForState(state_);
 
   if (icon == proximity_auth::ScreenlockBridge::USER_POD_CUSTOM_ICON_NONE) {
-    screenlock_bridge_->lock_handler()->HideUserPodCustomIcon(user_email_);
+    screenlock_bridge_->lock_handler()->HideUserPodCustomIcon(user_id_);
     return;
   }
 
@@ -185,7 +185,7 @@ void EasyUnlockScreenlockStateHandler::ChangeState(ScreenlockState new_state) {
         l10n_util::GetStringUTF16(IDS_SMART_LOCK_SPINNER_ACCESSIBILITY_LABEL));
   }
 
-  screenlock_bridge_->lock_handler()->ShowUserPodCustomIcon(user_email_,
+  screenlock_bridge_->lock_handler()->ShowUserPodCustomIcon(user_id_,
                                                             icon_options);
 }
 
@@ -248,7 +248,7 @@ void EasyUnlockScreenlockStateHandler::OnScreenDidUnlock(
 }
 
 void EasyUnlockScreenlockStateHandler::OnFocusedUserChanged(
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
 }
 
 void EasyUnlockScreenlockStateHandler::RefreshScreenlockState() {
@@ -267,7 +267,7 @@ void EasyUnlockScreenlockStateHandler::ShowHardlockUI() {
   // Do not override online signin.
   const proximity_auth::ScreenlockBridge::LockHandler::AuthType
       existing_auth_type =
-          screenlock_bridge_->lock_handler()->GetAuthType(user_email_);
+          screenlock_bridge_->lock_handler()->GetAuthType(user_id_);
   if (existing_auth_type ==
       proximity_auth::ScreenlockBridge::LockHandler::ONLINE_SIGN_IN)
     return;
@@ -275,13 +275,13 @@ void EasyUnlockScreenlockStateHandler::ShowHardlockUI() {
   if (existing_auth_type !=
       proximity_auth::ScreenlockBridge::LockHandler::OFFLINE_PASSWORD) {
     screenlock_bridge_->lock_handler()->SetAuthType(
-        user_email_,
+        user_id_,
         proximity_auth::ScreenlockBridge::LockHandler::OFFLINE_PASSWORD,
         base::string16());
   }
 
   if (hardlock_state_ == NO_PAIRING) {
-    screenlock_bridge_->lock_handler()->HideUserPodCustomIcon(user_email_);
+    screenlock_bridge_->lock_handler()->HideUserPodCustomIcon(user_id_);
     hardlock_ui_shown_ = false;
     return;
   }
@@ -322,7 +322,7 @@ void EasyUnlockScreenlockStateHandler::ShowHardlockUI() {
   }
   icon_options.SetTooltip(tooltip, true /* autoshow */);
 
-  screenlock_bridge_->lock_handler()->ShowUserPodCustomIcon(user_email_,
+  screenlock_bridge_->lock_handler()->ShowUserPodCustomIcon(user_id_,
                                                             icon_options);
   hardlock_ui_shown_ = true;
 }
@@ -373,7 +373,7 @@ void EasyUnlockScreenlockStateHandler::UpdateScreenlockAuthType() {
   // Do not override online signin.
   const proximity_auth::ScreenlockBridge::LockHandler::AuthType
       existing_auth_type =
-          screenlock_bridge_->lock_handler()->GetAuthType(user_email_);
+          screenlock_bridge_->lock_handler()->GetAuthType(user_id_);
   DCHECK_NE(proximity_auth::ScreenlockBridge::LockHandler::ONLINE_SIGN_IN,
             existing_auth_type);
 
@@ -381,7 +381,7 @@ void EasyUnlockScreenlockStateHandler::UpdateScreenlockAuthType() {
     if (existing_auth_type !=
         proximity_auth::ScreenlockBridge::LockHandler::USER_CLICK) {
       screenlock_bridge_->lock_handler()->SetAuthType(
-          user_email_,
+          user_id_,
           proximity_auth::ScreenlockBridge::LockHandler::USER_CLICK,
           l10n_util::GetStringUTF16(
               IDS_EASY_UNLOCK_SCREENLOCK_USER_POD_AUTH_VALUE));
@@ -389,7 +389,7 @@ void EasyUnlockScreenlockStateHandler::UpdateScreenlockAuthType() {
   } else if (existing_auth_type !=
              proximity_auth::ScreenlockBridge::LockHandler::OFFLINE_PASSWORD) {
     screenlock_bridge_->lock_handler()->SetAuthType(
-        user_email_,
+        user_id_,
         proximity_auth::ScreenlockBridge::LockHandler::OFFLINE_PASSWORD,
         base::string16());
   }