[Payments] Desktop: Error message in the dialog.

chrome/browser/payments/chrome_payment_request_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_PAYMENTS_CHROME_PAYMENT_REQUEST_DELEGATE_H_
 #define CHROME_BROWSER_PAYMENTS_CHROME_PAYMENT_REQUEST_DELEGATE_H_
 
 #include "base/macros.h"
 #include "components/payments/content/payment_request_delegate.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace payments {
 
 class PaymentRequest;
 class PaymentRequestDialog;
 
 class ChromePaymentRequestDelegate : public PaymentRequestDelegate {
  public:
   explicit ChromePaymentRequestDelegate(content::WebContents* web_contents);
   ~ChromePaymentRequestDelegate() override {}
 
   void ShowDialog(PaymentRequest* request) override;
   void CloseDialog() override;
+  void ShowErrorMessage() override;
   autofill::PersonalDataManager* GetPersonalDataManager() override;
   const std::string& GetApplicationLocale() const override;
   bool IsIncognito() const override;
 
  protected:
   // Reference to the dialog so that we can satisfy calls to CloseDialog(). This
   // reference is invalid once CloseDialog() has been called on it, because the
   // dialog will be destroyed. Protected for testing.
   PaymentRequestDialog* dialog_;
 
  private:
   // Not owned but outlives the PaymentRequest object that owns this.
   content::WebContents* web_contents_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromePaymentRequestDelegate);
 };
 
 }  // namespace payments
 
 #endif  // CHROME_BROWSER_PAYMENTS_CHROME_PAYMENT_REQUEST_DELEGATE_H_