[Payments] Show what's missing for incomplete payment methods.

chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc

Index: chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc
diff --git a/chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc b/chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc
index d0c10544c923c7d38cb9b4ac70d623534cc5e6a3..b5c735f585b7e6cef553aa325185b764d6bc84fd 100644
--- a/chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc
+++ b/chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc
@@ -204,8 +204,10 @@ bool CreditCardEditorViewController::ValidateModelAndSave() {
                         locale);
   }
 
-  // TODO(mathp): Display global error message.
-  if (!credit_card.IsValid())
+  // TODO(crbug.com/711365): Display global error message.
+  base::string16 error_message;
+  if (!autofill::IsCompleteForPaymentRequest(credit_card, locale,
+                                             &error_message))
     return false;
 
   if (!credit_card_to_edit_) {