[Payments] Change how the dialog gets destroyed.

chrome/browser/ui/views/payments/payment_request_dialog_view.h

Index: chrome/browser/ui/views/payments/payment_request_dialog_view.h
diff --git a/chrome/browser/ui/views/payments/payment_request_dialog_view.h b/chrome/browser/ui/views/payments/payment_request_dialog_view.h
index b79c877ad70055ec11a128cafb8214193119b1ba..cfacf1d209f38a258fa216e022c52196c894dd6d 100644
--- a/chrome/browser/ui/views/payments/payment_request_dialog_view.h
+++ b/chrome/browser/ui/views/payments/payment_request_dialog_view.h
@@ -114,7 +114,7 @@ class PaymentRequestDialogView : public views::DialogDelegateView,
   // a way of closing the dialog.
   void ShowProcessingSpinner();
 
-  ViewStack* view_stack_for_testing() { return &view_stack_; }
+  ViewStack* view_stack_for_testing() { return view_stack_.get(); }
 
  private:
   void ShowInitialPaymentSheet();
@@ -131,7 +131,7 @@ class PaymentRequestDialogView : public views::DialogDelegateView,
   // between the two.
   PaymentRequest* request_;
   ControllerMap controller_map_;
-  ViewStack view_stack_;
+  std::unique_ptr<ViewStack> view_stack_;
 
   // A full dialog overlay that shows a spinner and the "processing" label. It's
   // hidden until ShowProcessingSpinner is called.