Add a new region combo box model.

BUG=None

TBR=msw@
for trivial change in chrome\browser\ui\views\DEPS

Review-Url: https://codereview.chromium.org/2737553005
Cr-Commit-Position: refs/heads/master@{#456818}
diff --git a/chrome/browser/ui/views/payments/validating_combobox.h b/chrome/browser/ui/views/payments/validating_combobox.h
index 105759a..d001690 100644
--- a/chrome/browser/ui/views/payments/validating_combobox.h
+++ b/chrome/browser/ui/views/payments/validating_combobox.h
@@ -5,13 +5,17 @@
 #ifndef CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_COMBOBOX_H_
 #define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_COMBOBOX_H_
 
+#include <memory>
+
 #include "base/macros.h"
 #include "chrome/browser/ui/views/payments/validation_delegate.h"
+#include "ui/base/models/combobox_model_observer.h"
 #include "ui/views/controls/combobox/combobox.h"
 
 namespace payments {
 
-class ValidatingCombobox : public views::Combobox {
+class ValidatingCombobox : public views::Combobox,
+                           public ui::ComboboxModelObserver {
  public:
   ValidatingCombobox(std::unique_ptr<ui::ComboboxModel> model,
                      std::unique_ptr<ValidationDelegate> delegate);
@@ -24,6 +28,9 @@
   // Called when the combobox contents is changed. May do validation.
   void OnContentsChanged();
 
+  // ui::ComboboxModelObserver:
+  void OnComboboxModelChanged(ui::ComboboxModel* model) override;
+
  private:
   // Will call to the ValidationDelegate to validate the contents of the
   // combobox.