Modal window in user session not blocks user adding screen.

chrome/browser/ui/ash/session_state_delegate_chromeos.cc

Index: chrome/browser/ui/ash/session_state_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/session_state_delegate_chromeos.cc b/chrome/browser/ui/ash/session_state_delegate_chromeos.cc
index faba9736891ec75f6b9a218eb5bc7ad93657c3be..790de57222db8436bb7ba449d4f8042f47985688 100644
--- a/chrome/browser/ui/ash/session_state_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/session_state_delegate_chromeos.cc
@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "chrome/browser/chromeos/login/screen_locker.h"
 #include "chrome/browser/chromeos/login/user.h"
+#include "chrome/browser/chromeos/login/user_adding_screen.h"
 #include "chrome/browser/chromeos/login/user_manager.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
@@ -54,6 +55,11 @@ void SessionStateDelegateChromeos::UnlockScreen() {
   NOTIMPLEMENTED();
 }
 
+bool SessionStateDelegateChromeos::IsUserSessionBlocked() const {
+  return !IsActiveUserSessionStarted() || IsScreenLocked() ||
+         chromeos::UserAddingScreen::Get()->IsRunning();
+}
+
 const base::string16 SessionStateDelegateChromeos::GetUserDisplayName(
     ash::MultiProfileIndex index) const {
   DCHECK_LT(index, NumberOfLoggedInUsers());