[Payments] Add combobox support to editors.

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

Index: chrome/browser/ui/views/payments/preselected_combobox_model.h
diff --git a/chrome/browser/ui/views/payments/preselected_combobox_model.h b/chrome/browser/ui/views/payments/preselected_combobox_model.h
new file mode 100644
index 0000000000000000000000000000000000000000..8a1bb757a92b3b4308debe84e0263a3ff2ee5e0b
--- /dev/null
+++ b/chrome/browser/ui/views/payments/preselected_combobox_model.h
@@ -0,0 +1,35 @@
+// 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_PRESELECTED_COMBOBOX_MODEL_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_PRESELECTED_COMBOBOX_MODEL_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "ui/base/models/simple_combobox_model.h"
+
+namespace payments {
+
+// A simple data model for a combobox that takes a string16 vector as the items,
+// as well as the default selected index. An empty string is a separator.
+class PreselectedComboboxModel : public ui::SimpleComboboxModel {
+ public:
+  PreselectedComboboxModel(const std::vector<base::string16>& items,
+                           int default_index);
+  ~PreselectedComboboxModel() override;
+
+  // ui::ComboboxModel:
+  int GetDefaultIndex() const override;
+
+ private:
+  const int default_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreselectedComboboxModel);
+};
+
+}  // namespace payments
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_PRESELECTED_COMBOBOX_MODEL_H_