[Payment Request] Moves PaymentRequest into the payments namespace

ios/chrome/browser/ui/payments/payment_items_display_mediator.h

 // Copyright 2017 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 IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_ITEMS_DISPLAY_MEDIATOR_H_
 #define IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_ITEMS_DISPLAY_MEDIATOR_H_
 
 #import "ios/chrome/browser/ui/payments/payment_items_display_view_controller_data_source.h"
 
+namespace payments {
 class PaymentRequest;
+}  // namespace payments
 
 // Serves as data source for PaymentItemsDisplayViewController.
 @interface PaymentItemsDisplayMediator
     : NSObject<PaymentItemsDisplayViewControllerDataSource>
 
 // Initializes this object with an instance of PaymentRequest which has a copy
 // of web::PaymentRequest as provided by the page invoking the Payment Request
 // API. This object will not take ownership of |paymentRequest|.
-- (instancetype)initWithPaymentRequest:(PaymentRequest*)paymentRequest
+- (instancetype)initWithPaymentRequest:(payments::PaymentRequest*)paymentRequest
     NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_ITEMS_DISPLAY_MEDIATOR_H_