[Payment Request] Simplifies VC's logic to decide if an item is selectable

ios/chrome/browser/ui/payments/payment_request_selector_view_controller.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_REQUEST_SELECTOR_VIEW_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_REQUEST_SELECTOR_VIEW_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller.h"
 #import "ios/chrome/browser/ui/payments/payment_request_selector_view_controller_data_source.h"
 
 @class PaymentRequestSelectorViewController;
 
 // Delegate protocol for PaymentRequestSelectorViewController.
 @protocol PaymentRequestSelectorViewControllerDelegate<NSObject>
 
 // Notifies the delegate that the user has selected an item at the given index.
-- (void)paymentRequestSelectorViewController:
+// Returns whether the selection can actually be made.
+- (BOOL)paymentRequestSelectorViewController:
             (PaymentRequestSelectorViewController*)controller
                         didSelectItemAtIndex:(NSUInteger)index;
 
 // Notifies the delegate that the user has chosen to return to the previous
 // screen without making a selection.
 - (void)paymentRequestSelectorViewControllerDidFinish:
     (PaymentRequestSelectorViewController*)controller;
 
 @optional
 
@@ skipping 32 matching lines @@
 @property(nonatomic, assign, getter=isEditing) BOOL editing;
 
 // Convenience initializer. Initializes this object with the
 // CollectionViewControllerStyleAppBar style and sets up the leading (back)
 // button.
 - (instancetype)init;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_PAYMENTS_PAYMENT_REQUEST_SELECTOR_VIEW_CONTROLLER_H_