[Payments] Desktop: Error message in the dialog.

components/payments/content/payment_request_delegate.h

Index: components/payments/content/payment_request_delegate.h
diff --git a/components/payments/content/payment_request_delegate.h b/components/payments/content/payment_request_delegate.h
index dc421cdb4bc65b6ba98509511b59634299215fc4..98040a6aa575dc3d1de708ffcd1ec7e0841cf2d4 100644
--- a/components/payments/content/payment_request_delegate.h
+++ b/components/payments/content/payment_request_delegate.h
@@ -26,6 +26,10 @@ class PaymentRequestDelegate {
   // call when the dialog is not showing.
   virtual void CloseDialog() = 0;
 
+  // Disables the dialog and shows an error message that the transaction has
+  // failed.
+  virtual void ShowErrorMessage() = 0;
+
   // Gets the PersonalDataManager associated with this PaymentRequest flow.
   // Cannot be null.
   virtual autofill::PersonalDataManager* GetPersonalDataManager() = 0;