Remove DialogDelegate::UseNewStyle and unused code.

chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc

Index: chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
diff --git a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
index 0c99fec4012dcc0945f68fb70683e2a476b7a9a3..3020c7cc7860534f8046efdad65e51b8d9df2d9a 100644
--- a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
+++ b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
@@ -15,7 +15,6 @@
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
 #include "components/web_modal/web_contents_modal_dialog_manager_delegate.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/browser/web_contents_view.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/window_open_disposition.h"
@@ -59,9 +58,7 @@ TabModalConfirmDialogViews::TabModalConfirmDialogViews(
       web_contents_modal_dialog_manager->delegate();
   DCHECK(modal_delegate);
   dialog_ = views::Widget::CreateWindowAsFramelessChild(
-      this,
-      web_contents->GetView()->GetNativeView(),
-      modal_delegate->GetWebContentsModalDialogHost()->GetHostView());
+      this, modal_delegate->GetWebContentsModalDialogHost()->GetHostView());
   web_contents_modal_dialog_manager->ShowDialog(dialog_->GetNativeView());
   delegate_->set_close_delegate(this);
 }