Remove DialogDelegate::OnClosed() which is redundant with

ash/system/chromeos/session/logout_confirmation_dialog.cc

Index: ash/system/chromeos/session/logout_confirmation_dialog.cc
diff --git a/ash/system/chromeos/session/logout_confirmation_dialog.cc b/ash/system/chromeos/session/logout_confirmation_dialog.cc
index 80a71e84248a1dfda9e6b56a231dcaef55168f49..89c73b02476477bb35b58aed301c7faf8d1f3c32 100644
--- a/ash/system/chromeos/session/logout_confirmation_dialog.cc
+++ b/ash/system/chromeos/session/logout_confirmation_dialog.cc
@@ -84,15 +84,11 @@ base::string16 LogoutConfirmationDialog::GetDialogButtonLabel(
   return views::DialogDelegateView::GetDialogButtonLabel(button);
 }
 
-void LogoutConfirmationDialog::OnClosed() {
+void LogoutConfirmationDialog::WindowClosing() {
   update_timer_.Stop();
   controller_->OnDialogClosed();
 }
 
-void LogoutConfirmationDialog::DeleteDelegate() {
-  delete this;
-}
-
 void LogoutConfirmationDialog::UpdateLabel() {
   const base::TimeDelta time_remaining =
       logout_time_ - controller_->clock()->NowTicks();