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

chrome/browser/ui/views/payments/validation_delegate.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATION_DELEGATE_H_
 #define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATION_DELEGATE_H_
 
 namespace views {
 class Combobox;
 class Textfield;
 }  // namespace views
 
 namespace payments {
 
 class ValidationDelegate {
  public:
   virtual ~ValidationDelegate() {}
 
   // Only the delegate knows how to validate the textfield.
   virtual bool ValidateTextfield(views::Textfield* textfield) = 0;
 
   virtual bool ValidateCombobox(views::Combobox* combobox) = 0;
+  virtual void ComboboxModelChanged(views::Combobox* combobox) = 0;
 };
 
 }  // namespace payments
 
 #endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATION_DELEGATE_H_