chrome: Cleanup class/struct forward declarations

chrome/browser/sync_file_system/drive_backend/folder_creator.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_SYNC_FILE_SYSTEM_DRIVE_BACKEND_FOLDER_CREATOR_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_FOLDER_CREATOR_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/sync_file_system/sync_callbacks.h"
 #include "google_apis/drive/drive_api_error_codes.h"
 
 namespace drive {
 class DriveServiceInterface;
 }
 
 namespace google_apis {
 class FileList;
 class FileResource;
 }
 
 namespace sync_file_system {
 namespace drive_backend {
 
 class MetadataDatabase;
-class SyncEngineContext;
 
 class FolderCreator {
  public:
   typedef base::Callback<void(const std::string& file_id,
                               SyncStatusCode status)> FileIDCallback;
 
   FolderCreator(drive::DriveServiceInterface* drive_service,
                 MetadataDatabase* metadata_database,
                 const std::string& parent_folder_id,
                 const std::string& title);
@@ skipping 18 matching lines @@
 
   base::WeakPtrFactory<FolderCreator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FolderCreator);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_FOLDER_CREATOR_H_