Coordinators: let the presenting view controller dismiss.

ios/chrome/browser/payments/payment_request_coordinator.mm

 // 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.
 
 #import "ios/chrome/browser/payments/payment_request_coordinator.h"
 
 #include <unordered_set>
 #include <vector>
 
 #import "base/ios/weak_nsobject.h"
@@ skipping 94 matching lines @@
   _navigationController.reset([[UINavigationController alloc]
       initWithRootViewController:_viewController]);
   [_navigationController setNavigationBarHidden:YES];
 
   [[self baseViewController] presentViewController:_navigationController
                                           animated:YES
                                         completion:nil];
 }
 
 - (void)stop {
-  [_navigationController dismissViewControllerAnimated:YES completion:nil];
+  [[_navigationController presentingViewController]
+      dismissViewControllerAnimated:YES
+                         completion:nil];
   _itemsDisplayCoordinator.reset();
   _shippingAddressSelectionCoordinator.reset();
   _shippingOptionSelectionCoordinator.reset();
   _methodSelectionCoordinator.reset();
   _navigationController.reset();
   _viewController.reset();
 }
 
 - (std::vector<autofill::CreditCard*>)supportedMethods {
   std::vector<autofill::CreditCard*> supported_methods;
@@ skipping 206 matching lines @@
   _methodSelectionCoordinator.reset();
 }
 
 - (void)paymentMethodSelectionCoordinatorDidReturn:
     (PaymentMethodSelectionCoordinator*)coordinator {
   [_methodSelectionCoordinator stop];
   _methodSelectionCoordinator.reset();
 }
 
 @end