Cleanup: Remove forward declarations in various chrome/browser directories.

chrome/browser/printing/printer_query.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_PRINTER_QUERY_H_
 #define CHROME_BROWSER_PRINTING_PRINTER_QUERY_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/printing/print_job_worker_owner.h"
 #include "printing/print_job_constants.h"
 #include "ui/gfx/native_widget_types.h"
 
 class CancelableTask;
 class MessageLoop;
 
 namespace base {
 class DictionaryValue;
-class Thread;
 }
 
 namespace printing {
 
 class PrintJobWorker;
 
 // Query the printer for settings.
 class PrinterQuery : public PrintJobWorkerOwner {
  public:
   // GetSettings() UI parameter.
@@ skipping 68 matching lines @@
 
   // Task waiting to be executed.
   scoped_ptr<CancelableTask> callback_;
 
   DISALLOW_COPY_AND_ASSIGN(PrinterQuery);
 };
 
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_PRINTING_PRINTER_QUERY_H_