ash: Cleanup class/struct forward declarations

ash/shell/content/client/shell_main_delegate.h

 // Copyright (c) 2012 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 ASH_SHELL_CONTENT_CLIENT_SHELL_MAIN_DELEGATE_H_
 #define ASH_SHELL_CONTENT_CLIENT_SHELL_MAIN_DELEGATE_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/app/content_main_delegate.h"
 #include "content/shell/common/shell_content_client.h"
 
-namespace content {
-class ShellContentRendererClient;
-class ShellContentUtilityClient;
-}
-
 namespace ash {
 namespace shell {
 
 class ShellContentBrowserClient;
 
 class ShellMainDelegate : public content::ContentMainDelegate {
  public:
   ShellMainDelegate();
   ~ShellMainDelegate() override;
 
   bool BasicStartupComplete(int* exit_code) override;
   void PreSandboxStartup() override;
   content::ContentBrowserClient* CreateContentBrowserClient() override;
 
  private:
   void InitializeResourceBundle();
 
   std::unique_ptr<ShellContentBrowserClient> browser_client_;
   content::ShellContentClient content_client_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellMainDelegate);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_CONTENT_CLIENT_SHELL_MAIN_DELEGATE_H_