PaymentRequest: The currencySystem should be non-nullable.

components/payments/payment_request.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/payments/payment_request.h"
 
 #include "base/memory/ptr_util.h"
 #include "components/autofill/core/browser/personal_data_manager.h"
 #include "components/payments/payment_details_validation.h"
 #include "components/payments/payment_request_delegate.h"
@@ skipping 47 matching lines @@
   client_->OnError(payments::mojom::PaymentErrorReason::USER_CANCEL);
 }
 
 void PaymentRequest::OnError() {
   binding_.Close();
   manager_->DestroyRequest(this);
 }
 
 CurrencyFormatter* PaymentRequest::GetOrCreateCurrencyFormatter(
     const std::string& currency_code,
-    const base::Optional<std::string> currency_system,
+    const std::string& currency_system,
     const std::string& locale_name) {
   if (!currency_formatter_) {
     currency_formatter_.reset(
         new CurrencyFormatter(currency_code, currency_system, locale_name));
   }
 
   return currency_formatter_.get();
 }
 
 autofill::AutofillProfile* PaymentRequest::GetCurrentlySelectedProfile() {
@@ skipping 22 matching lines @@
       cards.begin(),
       cards.end(),
       [] (autofill::CreditCard* card) {
         return card->IsValid();
   });
 
   return first_complete_card == cards.end() ? nullptr : *first_complete_card;
 }
 
 }  // namespace payments