The User Manager should be backed by a special profile, not the guest one.

chrome/browser/ui/cocoa/profiles/user_manager_mac.mm

Index: chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
diff --git a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
index c70c851cd75e108b5c3f01000e61ea5859de3880..0ab4fd3be443636f4474201d564b6f8f9324e8c2 100644
--- a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
+++ b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
@@ -146,12 +146,12 @@ void UserManagerMac::Show(const base::FilePath& profile_path_to_focus,
     return;
   }
 
-  // Create the guest profile, if necessary, and open the User Manager
-  // from the guest profile.
-  profiles::CreateGuestProfileForUserManager(
+  // Create the User Manager profile, if necessary, and open the User Manager
+  // when the profile is ready.
+  profiles::CreateUserManagerProfile(
       profile_path_to_focus,
       tutorial_mode,
-      base::Bind(&UserManagerMac::OnGuestProfileCreated));
+      base::Bind(&UserManagerMac::OnUserManagerProfileCreated));
 }
 
 // static
@@ -166,9 +166,9 @@ bool UserManagerMac::IsShowing() {
 }
 
 // static
-void UserManagerMac::OnGuestProfileCreated(Profile* guest_profile,
-                                           const std::string& url) {
-  instance_ = new UserManagerMac(guest_profile);
+void UserManagerMac::OnUserManagerProfileCreated(Profile* profile,
+                                                 const std::string& url) {
+  instance_ = new UserManagerMac(profile);
   [instance_->window_controller_ showURL:GURL(url)];
 }