[Web Payments] Add PopMany and Size functions to ViewStack

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

 // 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.
 
 #include "chrome/browser/ui/views/payments/payment_request_dialog_view.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 134 matching lines @@
   request_->Pay();
 }
 
 void PaymentRequestDialogView::GoBack() {
   view_stack_->Pop();
 
   if (observer_for_testing_)
     observer_for_testing_->OnBackNavigation();
 }
 
+void PaymentRequestDialogView::GoBackToPaymentSheet() {
+  // This assumes that the Payment Sheet is the first view in the stack. Thus if
+  // there is only one view, we are already showing the payment sheet.
+  if (view_stack_->size() > 1)
+    view_stack_->PopMany(view_stack_->size() - 1);
+
+  if (observer_for_testing_)
+    observer_for_testing_->OnBackToPaymentSheetNavigation();
+}
+
 void PaymentRequestDialogView::ShowContactProfileSheet() {
   view_stack_->Push(
       CreateViewAndInstallController(
           ProfileListViewController::GetContactProfileViewController(
               request_->spec(), request_->state(), this),
           &controller_map_),
       /* animate */ true);
   if (observer_for_testing_)
     observer_for_testing_->OnContactInfoOpened();
 }
@@ skipping 150 matching lines @@
   // When a view that is associated with a controller is removed from this
   // view's descendants, dispose of the controller.
   if (!details.is_add &&
       controller_map_.find(details.child) != controller_map_.end()) {
     DCHECK(!details.move_view);
     controller_map_.erase(details.child);
   }
 }
 
 }  // namespace payments