[Payments] Added region load failure tolerance and tests to PR editor.

chrome/browser/ui/views/payments/validating_combobox.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/payments/validating_combobox.h"
 
 #include <utility>
 
 #include "ui/base/models/combobox_model.h"
 
@@ skipping 27 matching lines @@
   // before as part of a blur.
   if (!was_blurred_)
     return;
 
   Validate();
 }
 
 void ValidatingCombobox::OnComboboxModelChanged(
     ui::ComboboxModel* unused_model) {
   ModelChanged();
+  delegate_->ComboboxModelChanged(this);
 }
 
 void ValidatingCombobox::Validate() {
   // ValidateCombobox may have side-effects, such as displaying errors.
   SetInvalid(!delegate_->ValidateCombobox(this));
 }
 
 }  // namespace payments