storage: Cleanup class/struct forward declarations

storage/browser/blob/blob_url_request_job.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_BLOB_BLOB_URL_REQUEST_JOB_H_
 #define STORAGE_BROWSER_BLOB_BLOB_URL_REQUEST_JOB_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "net/http/http_byte_range.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_request_job.h"
 #include "storage/browser/blob/blob_reader.h"
 #include "storage/browser/storage_browser_export.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace net {
-class DrainableIOBuffer;
 class IOBuffer;
 }
 
 namespace storage {
 
 class BlobDataHandle;
 class FileStreamReader;
 class FileSystemContext;
 
 // A request job that handles reading blob URLs.
@@ skipping 41 matching lines @@
   std::unique_ptr<net::HttpResponseInfo> response_info_;
 
   base::WeakPtrFactory<BlobURLRequestJob> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BlobURLRequestJob);
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_BLOB_BLOB_URL_REQUEST_JOB_H_