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

chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h

Index: chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h
diff --git a/chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h b/chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h
index a70a4de394cc2ef16458a289cdb3b6bb85cb0dfb..e83655099baa676f9336ba3db18f2fc37754821e 100644
--- a/chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h
+++ b/chrome/browser/chromeos/login/session/restore_after_crash_session_manager_delegate.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/session_manager/core/session_manager.h"
+#include "components/user_manager/user_id.h"
 
 class Profile;
 
@@ -19,7 +20,7 @@ class RestoreAfterCrashSessionManagerDelegate
     : public session_manager::SessionManagerDelegate {
  public:
   RestoreAfterCrashSessionManagerDelegate(Profile* profile,
-                                          const std::string& login_user_id);
+                                          const user_manager::UserID& login_user_id);
   ~RestoreAfterCrashSessionManagerDelegate() override;
 
  protected:
@@ -27,11 +28,11 @@ class RestoreAfterCrashSessionManagerDelegate
   void Start() override;
 
   Profile* profile() { return profile_; }
-  const std::string& login_user_id() const { return login_user_id_; }
+  const user_manager::UserID& login_user_id() const { return login_user_id_; }
 
  private:
   Profile* profile_;
-  const std::string login_user_id_;
+  const user_manager::UserID login_user_id_;
 
   DISALLOW_COPY_AND_ASSIGN(RestoreAfterCrashSessionManagerDelegate);
 };