Resolve new GAIA flow's infinite loop.

chrome/browser/chromeos/login/existing_user_controller.cc

Index: chrome/browser/chromeos/login/existing_user_controller.cc
diff --git a/chrome/browser/chromeos/login/existing_user_controller.cc b/chrome/browser/chromeos/login/existing_user_controller.cc
index a32ffb68d48f7ebba48f1d22d3bda68c2516951e..aa9615b1e6b1bcb1f88d2ad8ff16260567373635 100644
--- a/chrome/browser/chromeos/login/existing_user_controller.cc
+++ b/chrome/browser/chromeos/login/existing_user_controller.cc
@@ -693,7 +693,10 @@ void ExistingUserController::WhiteListCheckFailed(const std::string& email) {
     ShowError(IDS_LOGIN_ERROR_WHITELIST, email);
   }
 
-  login_display_->ShowSigninUI(email);
+  if (StartupUtils::IsWebviewSigninEnabled())
+    login_display_->ShowSigninUI("");
+  else
+    login_display_->ShowSigninUI(email);
 
   if (auth_status_consumer_) {
     auth_status_consumer_->OnAuthFailure(