[Web Payments] Add PopMany and Size functions to ViewStack

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

Index: chrome/browser/ui/views/payments/payment_request_dialog_view.cc
diff --git a/chrome/browser/ui/views/payments/payment_request_dialog_view.cc b/chrome/browser/ui/views/payments/payment_request_dialog_view.cc
index eb88d2fea5b15b3b9ac5993e2952269ded2173d1..a698975cbe7942bbffcdc0dd0bd10916f93a0e17 100644
--- a/chrome/browser/ui/views/payments/payment_request_dialog_view.cc
+++ b/chrome/browser/ui/views/payments/payment_request_dialog_view.cc
@@ -152,6 +152,11 @@ void PaymentRequestDialogView::GoBack() {
     observer_for_testing_->OnBackNavigation();
 }
 
+void PaymentRequestDialogView::GoBackToPaymentSheet() {
+  if (view_stack_->size() > 1)

[Mathieu, 2017/04/13 16:55:23]

Add comment:

// 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.

[anthonyvd, 2017/04/13 20:22:58]

Done.

+    view_stack_->PopMany(view_stack_->size() - 1);
+}
+
 void PaymentRequestDialogView::ShowContactProfileSheet() {
   view_stack_->Push(
       CreateViewAndInstallController(