Resolve new GAIA flow's infinite loop.

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
index af7eed7a43ce5b3ac8e973d252c759bf532c4f8d..0968a13a4cd6f95b8bf3a57e1baf054eb9879d5c 100644
--- a/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
@@ -624,8 +624,9 @@ void GaiaScreenHandler::StartClearingCookies(
              profile_helper->GetSigninProfile());
   profile_helper->ClearSigninProfile(
       base::Bind(&GaiaScreenHandler::OnCookiesCleared,
-                 weak_factory_.GetWeakPtr(),
-                 on_clear_callback));
+                 weak_factory_.GetWeakPtr(), on_clear_callback),
+      StartupUtils::IsWebviewSigninEnabled() ? web_ui()->GetWebContents()
+                                             : nullptr);
 }
 
 void GaiaScreenHandler::OnCookiesCleared(