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

components/payments/core/autofill_payment_instrument.cc

Index: components/payments/core/autofill_payment_instrument.cc
diff --git a/components/payments/core/autofill_payment_instrument.cc b/components/payments/core/autofill_payment_instrument.cc
index 398edb70f90faf1fc894814e61755c95390ae106..c05a048806d06c51b40e18831459350651a2eda6 100644
--- a/components/payments/core/autofill_payment_instrument.cc
+++ b/components/payments/core/autofill_payment_instrument.cc
@@ -10,6 +10,7 @@
 #include "components/autofill/core/browser/autofill_data_util.h"
 #include "components/autofill/core/browser/autofill_type.h"
 #include "components/autofill/core/browser/field_types.h"
+#include "components/autofill/core/browser/validation.h"
 #include "components/autofill/core/common/autofill_clock.h"
 #include "components/payments/core/basic_card_response.h"
 #include "components/payments/core/payment_request_data_util.h"
@@ -17,20 +18,6 @@
 
 namespace payments {
 
-namespace {
-
-// Returns whether |card| has a non-empty number and cardholder name. Server
-// cards will have a non-empty number.
-bool CreditCardHasNumberAndName(const autofill::CreditCard& card,
-                                const std::string& app_locale) {
-  return !card.number().empty() &&
-         !card.GetInfo(autofill::AutofillType(autofill::CREDIT_CARD_NAME_FULL),
-                       app_locale)
-              .empty();
-}
-
-}  // namespace
-
 AutofillPaymentInstrument::AutofillPaymentInstrument(
     const std::string& method_name,
     const autofill::CreditCard& card,
@@ -67,17 +54,15 @@ void AutofillPaymentInstrument::InvokePaymentApp(
                                                weak_ptr_factory_.GetWeakPtr());
 }
 
-bool AutofillPaymentInstrument::IsCompleteForPayment() {
-  // A card is complete for payment if it's not expired, its number is not
-  // empty (a server card fills this condition) and there is a cardholder name.
-  // TODO(crbug.com/709776): Check for billing address association.
-  return !credit_card_.IsExpired(autofill::AutofillClock::Now()) &&
-         CreditCardHasNumberAndName(credit_card_, app_locale_);
+bool AutofillPaymentInstrument::IsCompleteForPayment(
+    base::string16* missing_info) {
+  return autofill::IsCompleteForPaymentRequest(credit_card_, app_locale_,
+                                               missing_info);
 }
 
 bool AutofillPaymentInstrument::IsValidForCanMakePayment() {
   // An expired card is still valid for the purposes of canMakePayment.
-  return CreditCardHasNumberAndName(credit_card_, app_locale_);
+  return autofill::CreditCardHasNumberAndName(credit_card_, app_locale_);
 }
 
 void AutofillPaymentInstrument::OnFullCardRequestSucceeded(