storage: Cleanup class/struct forward declarations

storage/browser/fileapi/file_system_file_stream_reader.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 STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_FILE_STREAM_READER_H_
 #define STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_FILE_STREAM_READER_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/files/file.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "storage/browser/blob/shareable_file_reference.h"
 #include "storage/browser/fileapi/file_stream_reader.h"
 #include "storage/browser/fileapi/file_system_url.h"
 #include "storage/browser/storage_browser_export.h"
 
 namespace base {
 class FilePath;
-class SequencedTaskRunner;
 }
 
 namespace content {
 class FileSystemFileStreamReaderTest;
 }
 
 namespace storage {
 
 class FileSystemContext;
 
@@ skipping 40 matching lines @@
   scoped_refptr<storage::ShareableFileReference> snapshot_ref_;
   bool has_pending_create_snapshot_;
   base::WeakPtrFactory<FileSystemFileStreamReader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemFileStreamReader);
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_FILE_STREAM_READER_H_