Add a basic demo mode browser test.

chrome/browser/chromeos/login/login_display_host_impl.h

Index: chrome/browser/chromeos/login/login_display_host_impl.h
diff --git a/chrome/browser/chromeos/login/login_display_host_impl.h b/chrome/browser/chromeos/login/login_display_host_impl.h
index 049da916b8b6ce78064b8fe8645b6d1c1e373b6f..4d84caf25941b6ae93b25d6f1ea4903c852968b9 100644
--- a/chrome/browser/chromeos/login/login_display_host_impl.h
+++ b/chrome/browser/chromeos/login/login_display_host_impl.h
@@ -13,7 +13,6 @@
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/chromeos/login/app_launch_controller.h"
 #include "chrome/browser/chromeos/login/auth_prewarmer.h"
-#include "chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h"
 #include "chrome/browser/chromeos/login/existing_user_controller.h"
 #include "chrome/browser/chromeos/login/login_display.h"
 #include "chrome/browser/chromeos/login/login_display_host.h"
@@ -39,6 +38,7 @@ class AutoEnrollmentClient;
 
 namespace chromeos {
 
+class DemoAppLauncher;
 class FocusRingController;
 class KeyboardDrivenOobeKeyHandler;
 class OobeUI;