Put PrintingUIWebContentsObserver and PrintingMessageFilter into printing namespace.

chrome/browser/printing/print_job_worker.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 CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_
 #define CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread.h"
 #include "printing/page_number.h"
 #include "printing/print_destination_interface.h"
 #include "printing/printing_context.h"
 #include "printing/print_job_constants.h"
 
-class PrintingUIWebContentsObserver;
-
 namespace base {
 class DictionaryValue;
 }
 
 namespace printing {
 
+class PrintJob;
+class PrintJobWorkerOwner;
 class PrintedDocument;
 class PrintedPage;
-class PrintJob;
-class PrintJobWorkerOwner;
+class PrintingUIWebContentsObserver;
 
 // Worker thread code. It manages the PrintingContext, which can be blocking
 // and/or run a message loop. This is the object that generates most
 // NOTIFY_PRINT_JOB_EVENT notifications, but they are generated through a
 // NotificationTask task to be executed from the right thread, the UI thread.
 // PrintJob always outlives its worker instance.
 class PrintJobWorker {
  public:
   explicit PrintJobWorker(PrintJobWorkerOwner* owner);
   virtual ~PrintJobWorker();
@@ skipping 118 matching lines @@
 
   // Used to generate a WeakPtr for callbacks.
   base::WeakPtrFactory<PrintJobWorker> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintJobWorker);
 };
 
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_JOB_WORKER_H_