[Payments] Add combobox support to editors.

chrome/browser/ui/views/payments/validating_combobox.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_VALIDATING_COMBOBOX_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_COMBOBOX_H_
+
+#include "base/macros.h"
+#include "chrome/browser/ui/views/payments/validation_delegate.h"
+#include "ui/views/controls/combobox/combobox.h"
+
+namespace payments {
+
+class ValidatingCombobox : public views::Combobox {
+ public:
+  explicit ValidatingCombobox(std::unique_ptr<ui::ComboboxModel> model,

[please use gerrit instead, 2017/02/15 15:59:39]

No need for "explicit" keyword with more than one parameter.

[Mathieu, 2017/02/15 19:55:51]

Done.

+                              std::unique_ptr<ValidationDelegate> delegate);
+  ~ValidatingCombobox() override;
+
+  // Combobox:
+  // The first validation will happen on blur.
+  void OnBlur() override;
+
+  // Called when the combobox contents is changed. May do validation.
+  void OnContentsChanged();
+
+ private:
+  // Will call to the ValidationDelegate to validate the contents of the
+  // combobox.
+  void Validate();
+
+  std::unique_ptr<ValidationDelegate> delegate_;
+  bool was_validated_ = false;

[please use gerrit instead, 2017/02/15 15:59:39]

Haven't see this done before. Perhaps it's best to init in the constructor,
where delegate_ is also being initialized.

[Mathieu, 2017/02/15 19:55:51]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(ValidatingCombobox);
+};
+
+}  // namespace payments
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_COMBOBOX_H_