Cleanup: Another round of unused forward declaration cleanup.

chrome/browser/printing/print_system_task_proxy.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_SYSTEM_TASK_PROXY_H_
 #define CHROME_BROWSER_PRINTING_PRINT_SYSTEM_TASK_PROXY_H_
 #pragma once
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop_helpers.h"
 #include "build/build_config.h"
 #include "content/public/browser/browser_thread.h"
 
 class PrintPreviewHandler;
 
 namespace base {
 class DictionaryValue;
-class StringValue;
 }
 
 namespace printing {
 class PrintBackend;
 struct PrinterCapsAndDefaults;
 }
 
 #if defined(UNIT_TEST) && defined(USE_CUPS) && !defined(OS_MACOSX)
 typedef struct cups_option_s cups_option_t;
 
@@ skipping 64 matching lines @@
   base::WeakPtr<PrintPreviewHandler> handler_;
 
   scoped_refptr<printing::PrintBackend> print_backend_;
 
   bool has_logged_printers_count_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintSystemTaskProxy);
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_SYSTEM_TASK_PROXY_H_