[Payments] Basic validation in the credit card editor.

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

Index: chrome/browser/ui/views/payments/validating_textfield.h
diff --git a/chrome/browser/ui/views/payments/validating_textfield.h b/chrome/browser/ui/views/payments/validating_textfield.h
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+++ b/chrome/browser/ui/views/payments/validating_textfield.h
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+// 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_TEXTFIELD_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_TEXTFIELD_H_
+
+#include "ui/views/controls/textfield/textfield.h"
+
+namespace payments {
+
+class ValidatingTextfield : public views::Textfield {
+ public:
+  class Delegate {
+   public:
+    // Only the delegate knows how to validate textfield.
+    virtual bool ValidateTextfield(ValidatingTextfield* textfield) = 0;
+  };
+
+  explicit ValidatingTextfield(ValidatingTextfield::Delegate* delegate);
+
+  // The first validation will happen on blur.
+  void OnBlur() override;
+
+  // Called when the textfield contents is changed. May do validation.
+  void OnContentsChanged();
+
+ private:
+  // Will call to the Delegate to validate the contents of the textfield.
+  void Validate();
+
+  ValidatingTextfield::Delegate* delegate_;
+  bool was_validated_ = false;
+};
+
+}  // namespace payments
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_VALIDATING_TEXTFIELD_H_