Added login screen mode for adding users into session.

chrome/browser/chromeos/login/login_display_host.h

Index: chrome/browser/chromeos/login/login_display_host.h
diff --git a/chrome/browser/chromeos/login/login_display_host.h b/chrome/browser/chromeos/login/login_display_host.h
index 15f4f6467908a3a44450e4532ceab8e59c70333a..06117c97902b1c5f707fa16d8ae546a93e63bd9d 100644
--- a/chrome/browser/chromeos/login/login_display_host.h
+++ b/chrome/browser/chromeos/login/login_display_host.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/customization_document.h"
@@ -46,9 +47,9 @@ class LoginDisplayHost {
   // Called when browsing session starts before creating initial browser.
   virtual void BeforeSessionStart() = 0;
 
-  // Called when browsing session starts so
+  // Called when user enters or returns to browsing session so
   // LoginDisplayHost instance may delete itself.
-  virtual void OnSessionStart() = 0;
+  virtual void Finalize() = 0;
 
   // Called when a login has completed successfully.
   virtual void OnCompleteLogin() = 0;
@@ -81,6 +82,11 @@ class LoginDisplayHost {
   // Result should not be stored.
   virtual WizardController* GetWizardController() = 0;
 
+  // Starts screen for adding user into session.
+  // |completion_callback| called before display host shutdown.
+  // |completion_callback| can be null.
+  virtual void StartUserAdding(const base::Closure& completion_callback) = 0;
+
   // Starts sign in screen.
   virtual void StartSignInScreen() = 0;