[Web Payments] Implement item selection in lists.

components/payments/content/payment_request_state.cc

Index: components/payments/content/payment_request_state.cc
diff --git a/components/payments/content/payment_request_state.cc b/components/payments/content/payment_request_state.cc
index 01b95a3f38d3347b2eb323fe3fff9d192100c4e5..26e8bf3d5f951169ceec6af0171c6db8a08d4eee 100644
--- a/components/payments/content/payment_request_state.cc
+++ b/components/payments/content/payment_request_state.cc
@@ -4,6 +4,8 @@
 
 #include "components/payments/content/payment_request_state.h"
 
+#include <set>
+
 #include "components/autofill/core/browser/autofill_data_util.h"
 #include "components/autofill/core/browser/autofill_profile.h"
 #include "components/autofill/core/browser/credit_card.h"
@@ -60,6 +62,12 @@ void PaymentRequestState::GeneratePaymentResponse() {
   selected_instrument_->InvokePaymentApp(this);
 }
 
+void PaymentRequestState::SetSelectedShippingOption(
+    mojom::PaymentShippingOption* option) {
+  selected_shipping_option_ = option;
+  UpdateIsReadyToPayAndNotifyObservers();
+}
+
 void PaymentRequestState::SetSelectedShippingProfile(
     autofill::AutofillProfile* profile) {
   selected_shipping_profile_ = profile;