arc: Fix DefaultApps flakiness

chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc
index 9810416578a8b5f084cf211ac398bdfa1252ff19..d2c0deae7b74640c5138086ea274b05cf3ea9e29 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller_impl_unittest.cc
@@ -3883,6 +3883,7 @@ TEST_F(ChromeLauncherControllerArcDefaultAppsTest, DefaultApps) {
   arc_test_.SetUp(profile());
   InitLauncherController();
   ChromeLauncherController::set_instance(launcher_controller_.get());
+  arc::ArcAuthService::SetShelfDelegateForTesting(launcher_controller_.get());
 
   ArcAppListPrefs* const prefs = arc_test_.arc_app_list_prefs();
   EnableArc(false);