[Web Payments] Implement the credit card selection UI functionality.

components/payments/payment_request.h

 // 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.
 
 #ifndef COMPONENTS_PAYMENTS_PAYMENT_REQUEST_H_
 #define COMPONENTS_PAYMENTS_PAYMENT_REQUEST_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 82 matching lines @@
 
   const std::vector<autofill::CreditCard*>& credit_cards() {
     return credit_cards_;
   }
 
   // Returns the currently selected credit card for this PaymentRequest flow.
   // It's not guaranteed to be complete. Returns nullptr if there is no selected
   // card.
   autofill::CreditCard* selected_credit_card() { return selected_credit_card_; }
 
+  void set_selected_credit_card(autofill::CreditCard* credit_card) {
+    selected_credit_card_ = credit_card;
+  }
+
   autofill::PersonalDataManager* personal_data_manager() {
     return delegate_->GetPersonalDataManager();
   }
 
   payments::mojom::PaymentDetails* details() { return details_.get(); }
   const std::vector<std::string>& supported_card_networks() {
     return supported_card_networks_;
   }
   content::WebContents* web_contents() { return web_contents_; }
 
@@ skipping 32 matching lines @@
   std::vector<std::unique_ptr<autofill::CreditCard>> card_cache_;
   std::vector<autofill::CreditCard*> credit_cards_;
   autofill::CreditCard* selected_credit_card_;
 
   DISALLOW_COPY_AND_ASSIGN(PaymentRequest);
 };
 
 }  // namespace payments
 
 #endif  // COMPONENTS_PAYMENTS_PAYMENT_REQUEST_H_