chrome: Cleanup class/struct forward declarations

chrome/browser/ui/ash/chrome_new_window_client.h

 // Copyright 2013 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_ASH_CHROME_NEW_WINDOW_CLIENT_H_
 #define CHROME_BROWSER_UI_ASH_CHROME_NEW_WINDOW_CLIENT_H_
 
 #include <memory>
 
 #include "ash/public/interfaces/new_window.mojom.h"
 #include "base/macros.h"
 
-class Browser;
-
 class ChromeNewWindowClient : public ash::mojom::NewWindowClient {
  public:
   ChromeNewWindowClient();
   ~ChromeNewWindowClient() override;
 
   // Overridden from ash::mojom::NewWindowClient:
   void NewTab() override;
   void NewWindow(bool incognito) override;
   void OpenFileManager() override;
   void OpenCrosh() override;
   void OpenGetHelp() override;
   void RestoreTab() override;
   void ShowKeyboardOverlay() override;
   void ShowTaskManager() override;
   void OpenFeedbackPage() override;
 
  private:
   class TabRestoreHelper;
 
   std::unique_ptr<TabRestoreHelper> tab_restore_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeNewWindowClient);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_CHROME_NEW_WINDOW_CLIENT_H_