net: Cleanup class/struct forward declarations

net/url_request/url_fetcher_response_writer.h

 // Copyright (c) 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 NET_URL_REQUEST_URL_FETCHER_RESPONSE_WRITER_H_
 #define NET_URL_REQUEST_URL_FETCHER_RESPONSE_WRITER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
 
 namespace base {
 class SequencedTaskRunner;
 }  // namespace base
 
 namespace net {
 
-class DrainableIOBuffer;
 class FileStream;
 class IOBuffer;
 class URLFetcherFileWriter;
 class URLFetcherStringWriter;
 
 // This class encapsulates all state involved in writing URLFetcher response
 // bytes to the destination.
 class NET_EXPORT URLFetcherResponseWriter {
  public:
   virtual ~URLFetcherResponseWriter() {}
@@ skipping 102 matching lines @@
 
   // Callbacks are created for use with base::FileUtilProxy.
   base::WeakPtrFactory<URLFetcherFileWriter> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(URLFetcherFileWriter);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_FETCHER_RESPONSE_WRITER_H_