Add Browser::SkipCallBeforeUnload so that the browser windows can be closed regardless of beforeunl…

chrome/browser/ui/unload_controller_web_contents_delegate.h

+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_UI_UNLOAD_CONTROLLER_WEB_CONTENTS_DELEGATE_H_
+#define CHROME_BROWSER_UI_UNLOAD_CONTROLLER_WEB_CONTENTS_DELEGATE_H_
+
+#include "content/public/browser/web_contents_delegate.h"
+
+// UnloadControllerWebContentsDelegate will delete web contents when they are
+// closed. It's used by UnloadController when beforeunload event is skipped so
+// that the existing dialogs will be closed as well. It's used by
+// FastUnloadController regardless.
+class UnloadControllerWebContentsDelegate
+    : public content::WebContentsDelegate {
+ public:
+  UnloadControllerWebContentsDelegate();
+  ~UnloadControllerWebContentsDelegate() override;
+
+  // WebContentsDelegate implementation.
+  bool ShouldSuppressDialogs(content::WebContents* source) override;
+  void CloseContents(content::WebContents* source) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UnloadControllerWebContentsDelegate);
+};
+
+#endif  // CHROME_BROWSER_UI_UNLOAD_CONTROLLER_WEB_CONTENTS_DELEGATE_H_