chrome: Cleanup class/struct forward declarations

chrome/browser/chromeos/fileapi/external_file_protocol_handler.h

 // Copyright 2014 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_CHROMEOS_FILEAPI_EXTERNAL_FILE_PROTOCOL_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_FILEAPI_EXTERNAL_FILE_PROTOCOL_HANDLER_H_
 
 #include "base/macros.h"
 #include "net/url_request/url_request_job_factory.h"
 
-namespace base {
-class SequencedTaskRunner;
-}  // namespace base
-
 namespace chromeos {
 
 class ExternalFileProtocolHandler
     : public net::URLRequestJobFactory::ProtocolHandler {
  public:
   explicit ExternalFileProtocolHandler(void* profile_id);
   ~ExternalFileProtocolHandler() override;
 
   // Creates URLRequestJobs for drive:// URLs.
   net::URLRequestJob* MaybeCreateJob(
       net::URLRequest* request,
       net::NetworkDelegate* network_delegate) const override;
 
  private:
   // The profile for processing Drive accesses. Should not be NULL.
   void* profile_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalFileProtocolHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILEAPI_EXTERNAL_FILE_PROTOCOL_HANDLER_H_