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

chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h

Index: chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h
diff --git a/chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h
index 4c85d4fe6c47c33aa3e27eddcc102e41b2dab285..38728598dd4975aaad3a2b851202e0a2ddceb248 100644
--- a/chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h
+++ b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_tpm_key_manager_factory.h
@@ -14,6 +14,10 @@ namespace content {
 class BrowserContext;
 }
 
+namespace user_manager {
+class UserID;
+}
+
 template <typename T> struct DefaultSingletonTraits;
 class EasyUnlockTpmKeyManager;
 
@@ -24,7 +28,7 @@ class EasyUnlockTpmKeyManagerFactory
   static EasyUnlockTpmKeyManagerFactory* GetInstance();
 
   static EasyUnlockTpmKeyManager* Get(content::BrowserContext* context);
-  static EasyUnlockTpmKeyManager* GetForUser(const std::string& user_id);
+  static EasyUnlockTpmKeyManager* GetForUser(const user_manager::UserID& user_id);
 
  private:
   friend struct DefaultSingletonTraits<EasyUnlockTpmKeyManagerFactory>;