[Payments] Record SelectedPaymentMethod metric on Desktop.

components/payments/content/payment_request.cc

Index: components/payments/content/payment_request.cc
diff --git a/components/payments/content/payment_request.cc b/components/payments/content/payment_request.cc
index 852d877f889932c288f0aa0fff98927d9600cc65..41ac5409766bb491ca639c5338742e32c75c9ff1 100644
--- a/components/payments/content/payment_request.cc
+++ b/components/payments/content/payment_request.cc
@@ -268,6 +268,8 @@ void PaymentRequest::OnConnectionTerminated() {
 }
 
 void PaymentRequest::Pay() {
+  journey_logger_.SetSelectedPaymentMethod(
+      JourneyLogger::SELECTED_PAYMENT_METHOD_CREDIT_CARD);
   state_->GeneratePaymentResponse();
 }