chrome: Cleanup class/struct forward declarations

chrome/browser/printing/print_job_worker_owner.h

 // Copyright (c) 2011 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_PRINTING_PRINT_JOB_WORKER_OWNER_H__
 #define CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_OWNER_H__
 
 #include <memory>
 
 #include "base/memory/ref_counted.h"
 #include "printing/printing_context.h"
 
 namespace base {
-class MessageLoop;
 class SequencedTaskRunner;
 }
 
 namespace tracked_objects {
 class Location;
 }
 
 namespace printing {
 
 class PrintJobWorker;
@@ skipping 35 matching lines @@
   virtual ~PrintJobWorkerOwner();
 
   // Task runner reference. Used to send notifications in the right
   // thread.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 };
 
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_OWNER_H__