Cleanup remaining class/struct fwd declarations

headless/public/util/in_memory_request_job.h

 // Copyright 2016 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 HEADLESS_PUBLIC_UTIL_IN_MEMORY_URL_REQUEST_JOB_H_
 #define HEADLESS_PUBLIC_UTIL_IN_MEMORY_URL_REQUEST_JOB_H_
 
 #include "base/memory/weak_ptr.h"
 #include "headless/public/util/in_memory_protocol_handler.h"
 #include "net/url_request/url_request_job.h"
 
-namespace net {
-class StringIOBuffer;
-class DrainableIOBuffer;
-}
-
 namespace headless {
 class InMemoryRequestJob : public net::URLRequestJob {
  public:
   InMemoryRequestJob(net::URLRequest* request,
                      net::NetworkDelegate* network_delegate,
                      const InMemoryProtocolHandler::Response* response);
 
   // net::URLRequestJob implementation:
   void Start() override;
   void Kill() override;
   int ReadRawData(net::IOBuffer* buf, int buf_size) override;
   bool GetMimeType(std::string* mime_type) const override;
 
  private:
   ~InMemoryRequestJob() override;
 
   void StartAsync();
 
   const InMemoryProtocolHandler::Response* response_;  // NOT OWNED
   size_t data_offset_;
 
   base::WeakPtrFactory<InMemoryRequestJob> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(InMemoryRequestJob);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_UTIL_IN_MEMORY_URL_REQUEST_JOB_H_