[Payment Request] Displays appropriate footer if first transaction completed

ios/chrome/browser/payments/payment_request.mm

Index: ios/chrome/browser/payments/payment_request.mm
diff --git a/ios/chrome/browser/payments/payment_request.mm b/ios/chrome/browser/payments/payment_request.mm
index 3885edb41feb6fa1fe4d4258cf40d3d8b8d62faf..091c41ceee644a6d9a158084b729eb4d60cda60a 100644
--- a/ios/chrome/browser/payments/payment_request.mm
+++ b/ios/chrome/browser/payments/payment_request.mm
@@ -18,10 +18,13 @@
 #include "components/payments/core/address_normalizer_impl.h"
 #include "components/payments/core/currency_formatter.h"
 #include "components/payments/core/payment_request_data_util.h"
+#include "components/prefs/pref_service.h"
+#include "components/signin/core/browser/signin_manager.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/autofill/validation_rules_storage_factory.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #import "ios/chrome/browser/payments/payment_request_util.h"
+#include "ios/chrome/browser/signin/signin_manager_factory.h"
 #include "ios/web/public/payments/payment_request.h"
 #include "third_party/libaddressinput/chromium/chrome_metadata_source.h"
 #include "third_party/libaddressinput/src/cpp/include/libaddressinput/source.h"
@@ -156,13 +159,16 @@ ukm::UkmRecorder* PaymentRequest::GetUkmRecorder() {
 }
 
 std::string PaymentRequest::GetAuthenticatedEmail() const {
-  NOTREACHED() << "Implementation is never used";
-  return std::string();
+  const SigninManager* signin_manager =
+      ios::SigninManagerFactory::GetForBrowserStateIfExists(browser_state_);
+  if (signin_manager && signin_manager->IsAuthenticated())
+    return signin_manager->GetAuthenticatedAccountInfo().email;
+  else
+    return std::string();
 }
 
 PrefService* PaymentRequest::GetPrefService() {
-  NOTREACHED() << "Implementation is never used";
-  return nullptr;
+  return browser_state_->GetPrefs();
 }
 
 void PaymentRequest::UpdatePaymentDetails(const web::PaymentDetails& details) {