chrome: Cleanup class/struct forward declarations

chrome/browser/sync_file_system/drive_backend/uninstall_app_task.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_UNINSTALL_APP_TASK_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_UNINSTALL_APP_TASK_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/sync_file_system/drive_backend/sync_task.h"
 #include "chrome/browser/sync_file_system/remote_file_sync_service.h"
 #include "chrome/browser/sync_file_system/sync_callbacks.h"
 #include "google_apis/drive/drive_api_error_codes.h"
 
 namespace drive {
 class DriveServiceInterface;
 }
 
 namespace sync_file_system {
 namespace drive_backend {
 
-class FileTracker;
 class MetadataDatabase;
 class SyncEngineContext;
-class TrackerSet;
 
 class UninstallAppTask : public ExclusiveTask {
  public:
   typedef RemoteFileSyncService::UninstallFlag UninstallFlag;
   UninstallAppTask(SyncEngineContext* sync_context,
                    const std::string& app_id,
                    UninstallFlag uninstall_flag);
   ~UninstallAppTask() override;
 
   void RunExclusive(const SyncStatusCallback& callback) override;
@@ skipping 15 matching lines @@
 
   base::WeakPtrFactory<UninstallAppTask> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UninstallAppTask);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_UNINSTALL_APP_TASK_H_