Refactor kiosk app launch to be part of login screen UI flow.

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h
index a82f621baf1fc97457b7b1d34f110344f2362f44..33d8915c7200f1e142a56c355c133fd2366b59e6 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h
@@ -157,6 +157,9 @@ class SigninScreenHandlerDelegate {
   // Signs out if the screen is currently locked.
   virtual void Signout() = 0;
 
+  // Login to kiosk mode for app with |app_id|.
+  virtual void LoginAsKioskApp(const std::string& app_id) = 0;
+
  protected:
   virtual ~SigninScreenHandlerDelegate() {}
 };
@@ -327,6 +330,7 @@ class SigninScreenHandler
   void HandleUpdateOfflineLogin(bool offline_login_active);
   void HandleShowLocallyManagedUserCreationScreen();
   void HandleFocusPod(const std::string& user_id);
+  void HandleLaunchKioskApp(const std::string& app_id);
 
   // Fills |user_dict| with information about |user|.
   static void FillUserDictionary(User* user,