Added login screen mode for adding users into session.

chrome/browser/chromeos/login/webui_login_display.cc

Index: chrome/browser/chromeos/login/webui_login_display.cc
diff --git a/chrome/browser/chromeos/login/webui_login_display.cc b/chrome/browser/chromeos/login/webui_login_display.cc
index e72d46756c79db1e5c92eed95db6b2563052a219..3a6ff085e7cebb8d892dd0194c6d29aafb72a30a 100644
--- a/chrome/browser/chromeos/login/webui_login_display.cc
+++ b/chrome/browser/chromeos/login/webui_login_display.cc
@@ -8,6 +8,7 @@
 #include "chrome/browser/chromeos/accessibility/accessibility_util.h"
 #include "chrome/browser/chromeos/login/login_display_host_impl.h"
 #include "chrome/browser/chromeos/login/screen_locker.h"
+#include "chrome/browser/chromeos/login/user_adding_screen.h"
 #include "chrome/browser/chromeos/login/wallpaper_manager.h"
 #include "chrome/browser/chromeos/login/webui_login_view.h"
 #include "chrome/browser/profiles/profile_manager.h"
@@ -220,6 +221,14 @@ void WebUILoginDisplay::CancelPasswordChangedFlow() {
     delegate_->CancelPasswordChangedFlow();
 }
 
+void WebUILoginDisplay::CancelUserAdding() {
+  if (!UserAddingScreen::Get()->IsRunning()) {
+    LOG(ERROR) << "User adding screen not running.";
+    return;
+  }
+  UserAddingScreen::Get()->Cancel();
+}
+
 void WebUILoginDisplay::CreateAccount() {
   DCHECK(delegate_);
   if (delegate_)