chrome: Cleanup class/struct forward declarations

chrome/browser/chromeos/drive/fileapi/async_file_util.h

 // Copyright 2014 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_CHROMEOS_DRIVE_FILEAPI_ASYNC_FILE_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILEAPI_ASYNC_FILE_UTIL_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "storage/browser/fileapi/async_file_util.h"
 
 namespace drive {
 
-class FileSystemInterface;
-
 namespace internal {
 
 // The implementation of storage::AsyncFileUtil for Drive File System.
 class AsyncFileUtil : public storage::AsyncFileUtil {
  public:
   AsyncFileUtil();
   ~AsyncFileUtil() override;
 
   // storage::AsyncFileUtil overrides.
   void CreateOrOpen(
@@ skipping 63 matching lines @@
       const CreateSnapshotFileCallback& callback) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AsyncFileUtil);
 };
 
 }  // namespace internal
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILEAPI_ASYNC_FILE_UTIL_H_